I had some games specifically-recommended for you:
https://www.gog.com/forum/general/games_that_treat_gog_customers_as_second_class_citizens_v2

BTW, I had made efforts to inform the developer, which was definitely not so-called "wild shrieking".
https://www.gog.com/forum/ozymandias_bronze_age_empire_sim/season_pass_and_dlcs
https://twitter.com/ys_falcon/status/1603717256550223874
Two month had passed, nothing really changes on GOG; in contrast, the second DLC is available on Steam.
This is when I decide to warn the potential buyers about the issue.

All in all, I paid to enjoy the game, not to be disappointed by technical issues. Maybe you're born different. :)

That makes it even less "abandoned". According to that, the dev says "progress has been made but it is very slow. We are waiting to hear back from the GOG dev team", and that was only a couple weeks ago. And yet here you are shrieking about "DO NOT BUY ON GOG IT'S ABANDONED" when 1) it's not, they are updating it, 2) they are actively taking steps to get the DLC here. We all know GOG has issues with communication and some technical issues with getting DLC and other things to work. If that's how you treat devs who are putting up with GOG and making an effort to do the right thing, you are definitely "born different", that's for sure.

Are you guys arguing just about some missing extra map ?

Yah, they have been missing since 12/9 last year.

Yeah, you're "merely warning" them by falsely telling people the game is "abandoned." If you were rational and said that the DLC isn't here yet but the devs are working with GOG to resolve it, I would never have said anything. And you should know with GOG's history that it can take way more than a couple weeks. Do you think you can behave better in the future?

By the way, I have a number of games where I bought little or no DLC that's available, because they were fine without it. That's why it's DLC instead of part of the game: it's optional stuff. If you're one of those people who insist on "complete" games with tons of DLC you'll never even play because you fell victim to the "gotta get 'em all" marketing malarkey, I can only suggest seeing a therapist. It's possible I might want extra maps for Ozymandias in the future, and I do expect the devs and GOG to work things out with the DLC technical issues, but for now I'm fine, thanks.

Fine, then, "abandoned" may not be the most precise way to describe.
"secondarily-prioritized" or "partially-updated" is the better word.
Still, if someone buy the maingame on GOG, they lose the opportunity to buy the DLC till now. That is the main problem I care. Of course, the DLCs are optional, but the customers on GOG have no option to buy them till now.
In order to access them, neither playing the pirated game with DLC included nor buying the maingame again on another platform was a appropriate choice. You are fine and not falling into this dilemma because you does not want to buy the DLCs now.

And also,"GOG's history that it can take way more than a couple weeks." should not be taken as a natural thing.

No. They're waiting for GOG. What else do you expect them to do? Here we are again:

"progress has been made but it is very slow. We are waiting to hear back from the GOG dev team"

What about that is so hard for you to understand? This isn't the first time devs have had issues with DLC on GOG. Yes! That's it, that's all you had to say. Instead of blaming devs for something not their fault. Right, it shouldn't be, but that's the way it is. Maybe you can somehow get GOG to be better about communication and handling things in a timely manner, but nobody else has so far.

When did I blame the developer "only"? I only said the game was not updated appropriately on GOG, so people should not buy here. GOG, developer, and publisher all have the responsibility to properly maintain the game on the platform. Even GOG api was the source of the problem, the second DLC was still released on Steam. Meanwhile, the problem on GOG was still not solved yet. This consequences was surely not made without the developer.
In other words, only GOG had fault for the missing of the 1st DLC. And, both GOG and the developer had fault for the missing of the 2nd DLC.
In conclusion, both GOG and the developer have fault, but on different aspects.

Nope, that makes no sense at all; it's only GOG. If the devs need info from GOG to get the DLC to work, they can't do anything until they have that info. That's simple, basic logic. Not to mention the game had 4 & 5 star ratings before the DLC even existed...the gameplay didn't somehow become worse just because you can't currently buy a couple extra maps on GOG.