Through means "not direct". ;-)

I can think of many many reasons... If I felt like writing an article, I'd list them all! ;-P
Here's an example: you buy an old game on GOG that needs Direct Draw activated in Windows 10. If you don't do it, then the game won't run. GOG actually mentions such things on the game specific support pages.

It's never been easier than now. A few decades ago, I visited the library to borrow a big MS-DOS book to learn how to free up 622K (or something like that) of base RAM.

It's not impossible to get it run, but maybe for the OP it is. Next time, read the label on the bottle of poison before drinking it. (label here = OS support, mentioned on the game page)

Runs good here via Galaxy install, im rocking win10 1909, i don't think i could handle life without a working Wizardry 8.... it scratches my old school itch better then any other game.

Which version? Do you have the pre made characters? I tried this a few weeks back, having the old installer and the new one, installed one after the other. Major differences:
Old version worked flawlessly and had a whole load of premade characters.
New version made the sound card screech, didn’t have the pre made characters, then crashed on game start.

Same here. For me the game runs flawesly and smooth and no sound problems, via Galaxy or launchin externally. And of course there are premade characters to start with when you select new game.

I works for me under opengl or nglide

I remark. The installed copy is the one Galaxy installs by default.

Right, let me try this again.
I am !!NOT!! talking about Galaxy or the Game Version (which is 1.2.4 in both cases).

So, OFFLINE installer setup_wizardry8_2.0.0.6.exe, which is no longer available under the download offline installers on the website, but which I have backed up works flawlessly. It also contains prebuilt characters and a Saves folder already in place. It also plays the movies fine and launches correctly.

setup_wizardry_8_2001_12_23_(22306).exe which is the one now available on the website for download has the following issues:
It screetches at each movie start.
It opens with resolution 1024*, whereas the previous one opened full screen.
It does not play the start movie, nor does it start the game, just crashes at that point.
The instal does not contain a Saves folder, has no premade characters.

I will add this information to the main thread, and wishlist and other links here:
https://www.gog.com/forum/general/provide_a_full_and_complete_changelogged_download_system

I can repeat the above as many times as needed, all exactly the same issues. Here is a directory listing of the two versions, which quite clearly show the second one is missing the Saves folder completely, and has a different size. As the game version has not changed, GOG have changed something between the two versions and removed content. I have asked GOG about this, they reply with the standard "use galaxy to be able to roll back":

setup_wizardry8_2.0.0.6.exe:
---
Volume in drive C is Windows
Volume Serial Number is

Directory of C:\MyGames\Wizardry 8

10/05/2020 10:58 <DIR> .
10/05/2020 10:58 <DIR> ..
15/10/1999 18:07 1,105,408 3DfxSpl.dll
15/10/1999 18:14 1,105,408 3DfxSpl2.dll
15/10/1999 18:21 1,105,408 3DfxSpl3.dll
10/12/2001 20:49 102,454 3DSetup.exe
20/03/2013 14:39 55 3DVideo.CFG
15/01/2001 13:41 286,208 binkw32.dll
15/01/2001 18:08 0 CD.ROM
10/05/2020 10:48 <DIR> Data
10/05/2020 10:49 <DIR> Dll
10/05/2020 10:49 7,732 EULA.txt
14/09/2012 13:56 96,264 GameuxInstallHelper.dll
21/05/2013 16:51 128,352 gfw_high.ico
15/02/2013 21:27 1,290,240 glide.dll
02/04/2013 16:20 1,302,528 glide2x.dll
15/02/2013 21:29 1,318,912 glide3x.dll
14/09/2012 13:56 69,248 gog.ico
24/05/2013 13:06 283,968 goggame.dll
10/05/2020 10:49 1,574 Launch Wizardry 8.lnk
10/05/2020 10:49 <DIR> Levels
16/10/2001 16:56 125,952 Mp3dec.asi
16/10/2001 16:55 348,160 Mss32.dll
16/10/2001 16:56 52,224 Mssa3d.m3d
16/10/2001 16:56 61,952 Mssa3d2.m3d
16/10/2001 16:56 65,536 Mssdolby.m3d
16/10/2001 16:56 51,200 Mssds3dh.m3d
16/10/2001 16:56 50,688 Mssds3ds.m3d
16/10/2001 16:56 51,712 Mssdx7sh.m3d
16/10/2001 16:56 51,712 Mssdx7sl.m3d
16/10/2001 16:56 51,712 Mssdx7sn.m3d
16/10/2001 16:56 54,272 Msseax.m3d
16/10/2001 16:56 70,144 Msseax2.m3d
16/10/2001 16:56 64,000 Mssfast.m3d
16/10/2001 16:56 354,304 Mssrsx.m3d
16/10/2001 16:57 142,848 Mssv12.asi
16/10/2001 16:57 134,144 Mssv24.asi
16/10/2001 16:57 161,280 Mssv29.asi
15/01/2001 13:41 77,878 MSVCIRT.DLL
15/01/2001 13:41 401,462 MSVCP60.DLL
15/01/2001 13:41 266,293 MSVCRT.DLL
10/05/2020 10:58 0 mytemp.txt
06/12/2012 14:32 227 nGlideEULA.txt
02/04/2013 17:11 53,248 nglide_config.exe
02/04/2013 17:11 15,179 nglide_readme.txt
10/05/2020 10:49 <DIR> Patches
10/05/2020 10:49 <DIR> Saves
13/09/2001 20:09 688,191 sr.dll
14/09/2012 13:56 62,895 Support.ico
10/05/2020 10:49 239,256 unins000.dat
10/05/2020 10:47 1,233,216 unins000.exe
10/05/2020 10:49 1,009 unins000.ini
10/05/2020 10:49 22,733 unins000.msg
20/03/2013 14:06 2,063 Wiz8.CFG
24/12/2001 02:01 3,580,513 Wiz8.exe
06/10/1997 04:11 2,238 Wiz8.ico
26/12/2001 14:34 6,188 Wiz8Patch2001_12_23_README.txt
10/05/2013 12:11 591,849 Wizardry 8 - Manual.pdf
51 File(s) 17,340,037 bytes
---

setup_wizardry_8_2001_12_23_(22306).exe:
Volume in drive C is Windows
Volume Serial Number is

Directory of C:\MyGames\Wizardry 8

10/05/2020 11:12 <DIR> .
10/05/2020 11:12 <DIR> ..
10/05/2020 11:10 1,105,408 3DfxSpl.dll
10/05/2020 11:10 1,105,408 3DfxSpl2.dll
10/05/2020 11:10 1,105,408 3DfxSpl3.dll
10/05/2020 11:10 102,454 3DSetup.exe
10/05/2020 11:11 55 3DVideo.CFG
10/05/2020 11:10 286,208 binkw32.dll
06/03/2018 13:27 0 CD.ROM
10/05/2020 11:11 <DIR> Data
10/05/2020 11:10 <DIR> Dll
10/05/2020 11:11 36,796 EULA.txt
10/05/2020 11:10 1,527,808 glide.dll
10/05/2020 11:10 1,617,920 glide2x.dll
10/05/2020 11:10 1,712,128 glide3x.dll
09/08/2017 16:28 69,248 gog.ico
10/05/2020 11:11 3,112 goggame-1207659230.hashdb
10/05/2020 11:10 128,352 goggame-1207659230.ico
10/05/2020 11:11 1,214 goggame-1207659230.info
10/05/2020 11:11 1,615 goggame-1207659230.script
10/05/2020 11:11 631 goglog.ini
10/05/2020 11:11 1,592 Launch Wizardry 8.lnk
10/05/2020 11:11 <DIR> Levels
10/05/2020 11:10 125,952 Mp3dec.asi
10/05/2020 11:10 348,160 Mss32.dll
10/05/2020 11:10 52,224 Mssa3d.m3d
10/05/2020 11:10 61,952 Mssa3d2.m3d
10/05/2020 11:10 65,536 Mssdolby.m3d
10/05/2020 11:10 51,200 Mssds3dh.m3d
10/05/2020 11:10 50,688 Mssds3ds.m3d
10/05/2020 11:10 51,712 Mssdx7sh.m3d
10/05/2020 11:10 51,712 Mssdx7sl.m3d
10/05/2020 11:10 51,712 Mssdx7sn.m3d
10/05/2020 11:10 54,272 Msseax.m3d
10/05/2020 11:10 70,144 Msseax2.m3d
10/05/2020 11:10 64,000 Mssfast.m3d
10/05/2020 11:10 354,304 Mssrsx.m3d
10/05/2020 11:10 142,848 Mssv12.asi
10/05/2020 11:10 134,144 Mssv24.asi
10/05/2020 11:10 161,280 Mssv29.asi
10/05/2020 11:10 77,878 MSVCIRT.DLL
10/05/2020 11:10 401,462 MSVCP60.DLL
10/05/2020 11:10 266,293 MSVCRT.DLL
10/05/2020 11:12 0 mytemp.txt
10/05/2020 11:10 227 nGlideEULA.txt
10/05/2020 11:10 348,160 nglide_config.exe
10/05/2020 11:10 23,016 nglide_readme.txt
10/05/2020 11:10 <DIR> Patches
10/05/2020 11:10 688,191 sr.dll
09/08/2017 16:28 62,895 support.ico
10/05/2020 11:11 1,741,516 unins000.dat
10/05/2020 11:11 1,334,880 unins000.exe
10/05/2020 11:11 41 unins000.ini
10/05/2020 11:11 23,077 unins000.msg
18/07/2018 12:25 313,764 webcache.zip
10/05/2020 11:11 2,063 Wiz8.CFG
10/05/2020 11:10 3,580,513 Wiz8.exe
10/05/2020 11:10 2,238 Wiz8.ico
10/05/2020 11:10 6,188 Wiz8Patch2001_12_23_README.txt
10/05/2020 11:10 591,849 Wizardry 8 - Manual.pdf
54 File(s) 20,161,448 bytes

Whle they make their changes in the offline installer one thing you can do is use Galaxy to verify integrity files. That way the game should be sanitized or updated. Also that could be useful to see wich files are changed or updated in case that the two versions are not the same.

You are effectively repeating what support said, use the "optional" client. Which is a totally invalid answer. Galaxy is supposed to be optional, I do not want to use a client, ever, nor will ever have one installed. I want to be able to access the correct and working files as they have promised and not fulfilling, to provide. Its not just this game, the updates haven't worked well for a long time, website downloads are hidden, and often forgotten about, and offline installers often have unwanted bits in them, check out the deus ex release recently.
Simply put, the offline installers, and the methods of downloading them need a complete and total overhaul to be functioning. Otherwise, if I need to use a client I will just go over to steam where their client works, they are cheaper, and have a bigger catalog.

Well, You do not have to launch your game through Galaxy, you would use Galaxy to import your installation folder, verify it and/or update it. Then you can ignore Galaxy again, forever.
But who knows, maybe, later, you discover the advantages of download your offline installer through Galaxy extras, this is, the feature of the old GOG Downloader.

Sorry, I do not need a galaxy sales pitch. It is OPTIONAL. The problem is that GOG is not providing the service they should provide, that needs fixing. I did not use the GOG downloader, browser downloads are fine, I have NO problem with downloading, simply that GOG do not provide the working files, and do not provide the correct mechanisms for accessing working files. What is so difficult to understand here?

Speaking as a regular Galaxy user (ever since the closed Beta) I can understand your point.
I can easily accept the option of using Galaxy as a sort of download manager (in order to download + backup the installers).
But being "forced" to use Galaxy in order to manage a game (installing or uninstalling updates, etc) is completely unacceptable to me. These sort of things should always be availabe through the browser.

I play all my games (except the ones on my laptop) through Galaxy. But people who don't use the client should not feel like they have to use it in order to manage certain functionalities. That's what valve does. And that's exactly why I never bothered to create a steam account.

If you do not want to use a temporal workaround until an installer is fixed officially, Ok it is fine. But Be careful with the pitch you are using with someone that is just trying to give a different option as help.

Wait for the the new installer. You have opened a ticket for GOG, right? Then problem solved.

Did you read anything that I have posted? If you had you would see why I am getting annoyed. The installer has been like this since 2018. The “workaround” or continual pressure to use their client is unacceptable. I do not have a problem as I have backups, however there are several forum threads on this issue, tickets have been raised and the answer has been use galaxy, which is unacceptable. The download system in general is a debacle, I linked the thread above. Again the response has been use galaxy, again, unacceptable.

You are being unhelpful continually trying to push galaxy to someone else no clearly does not want to use it, and supporting GOG in both not fixing those things they should do, and validating their continuous two tier system of those who use galaxy and those who do not. My posts above have clearly shown there are problems and even shown where those problems are. You have replied twice completely ignoring the point, or what I have posted all to push galaxy. So this is why my tone is changing, and again I repeat, I do not what to use an “optional” client to fix something that has been broken for years.

OK so I grabbed the EXE from the server, removed galaxy form my system and installed the offline version. The data below is from the json of the archive hosted on GOG.

The game installed perfectly on my win10 x64 1909 system. Ran form Wiz8.exe which launched the 3dfx wrapper (nGlide, Version: 2.00) as intended and it launched without issue. That said your old installer might have an older broken wrapper and you need to update it. Images attached below this post to verify It's working, 60FPS too! nGlide is now at 2.10 for the latest version

setup_wizardry_8_2001_12_23_(22306).exe

-- Wizardry 8 --

title.......... wizardry_8
genre.......... Role-playing
game id........ 1207659230
url............ https://www.gog.com/game/wizardry_8
user rating.... 94%
release date... May 22, 2013

game items.....:

..standalone...:

[setup_wizardry_8_2001_12_23_(22306).exe] -- Wizardry 8
version: 2001_12_23

extras.........:

[wizardry_8_manuals.zip] -- manual
[wizardry_8_wallpaper.zip] -- wallpaper
[wizardry_8_soundtrack.zip] -- soundtrack (MP3)
[wizardry_8_ost_flac.zip] -- soundtrack (FLAC)
[wizardry_8_avatar.zip] -- avatar

changelog......:

#### Internal Update (23 July 2018)

* [WIN] updated internal installer structure, no changes to game files

* * *

#### Update (12 February 2018)

* We've updated the Mac version of Wizardry 8 to be compatible with Mac OS X 10.13.3 "High Sierra".

* * *

#### Update (08 February 2016)

* We've updated the Mac version of Wizardry 8 to be compatible with Mac OS X 10.11 "El Capitan".