Achievements I can safely say are a non-issue for most here
I disagree. GOG allowing games onto its store, while knowing they lack feature parity with the same game as other platforms, that is a token example of GOG allowing their own customers to be treated like second-class citizens.
I've been informally boycotting all games that do that for years.
That's a very big issue, and one that GOG needs to rectify.
Also, wanting feature parity, including Achievements, is not equivalent to wanting "more development on Galaxy 2.0," although your post conflates those different things as if
they are the same thing, even though they aren't.
GOG should in fact disallow games that lack feature parity, unless there are good technical reasons for why the features have to be removed on the GOG version, which there never is when it comes to Achievements (they are missing solely
due to the devs being both cheap & lazy & unethical, and GOG's complacency in allowing them to get away with it).