I agree 100% that the offline installers, combined with the OS's supported, should offer everything you need to play the game. I am not techy enough t get into the specifics of that, but I agree with the statement.

I was only commenting on the idea that GOG selling old games inherently implied they should put work into having them work on old OSes. I do not think that is the case, and indeed is kind of the opposite of the stated goal.

Fair point in terms of the confusion, especially with that being the very first item in the store submenu.
But there is the fact that the category includes 1452 titles (1368 without DLCs and extras) out of 7688 (5079 without DLCs and extras), so under 19% (just under 27% without DLCs and extras)... And that's despite odd inclusions like Bright Memory: Infinite, Snowtopia, Tormented Souls and The Invisible Hand.
But when it comes to GOG's "true identity"... It has none, unfortunately. It had one for its first few years, as Good Old Games, then for some two more years, until the "good news", it was that store with values, then I guess it remained just that bigger DRM-free store, until more recently when they even redefined what DRM-free for single player means...

They can't snap their fingers and make more old games clear their licensing issues. They can't snap their fingers and make more AAA publishers willing to sell their games DRM free. They can't snap their fingers and make the Average Joe care less about having all their games in one place (Steam). I don't know what people expect them to do.

Every piece of hardware will eventually fail at some point. What will you do with your boxed physical games then?

Emulators and other means to make old games run on modern machines is a much more future-proof method. Then I can rest (more) assured that my existing games will run also on my next PC, even if it has no e.g. optical drive to install and run boxed games. You could still buy an USB DVD-RW drive, but I've heard they don't necessarily work right with all sorts of old CD/DVD copy protection methods.

Sell them on the retro market for insance prices :D
My Voyager Borg Cube is worth 500€ and I payed 120€for Turrican 2 DOS.

The drives are ok. USB or not doesn't really matter. But modern Windows versions don't allow certain types of access or copy protection drivers like Tages.

It was a pain when it still worked, so I usually cracked my originals anyway.

I agree, emulators and virtual machines will be the future. Thanks to AMD we can still run 32 Bit software on our computers, but at some point I think those will have to be emulated just as 16 Bit DOS and Windows 3.11 software, depending on how long 64 Bit architecture will remain the way to go.