I know what you mean, but I think there are two levels of 'bad'. I didn't enjoy Game of Thrones (the books, never bothered with the show because I didn't like the books) but I can see that there is something there that others might enjoy. I think it's bad, but it's not objectively bad.
On the other hand there are books I've read were the author was barely literate and everything was a bad cliche, every twist predictable etc. They are objectively bad, badly written. I don't think we need 100s (if not 1000s) of books, games, movies etc. that don't pass that basic talent mark.
TV and Movies don't suffer this issue (yet anyway, probably never) because the bar to entry is far too high. You might be able to make a pilot for your badly written awful idea but it will never likely see the light of day as a full series unless you are a millionaire who can fund it personally. Sure, there is bad TV still, of course there is, but not in the same way there are bad books and bad games.
More importantly, no matter how hard GOG tries, Steam is still pretty much the main marketplace for PC gaming, which means that it's the first place people want to release and the first place most people look for games. With tens to hundreds of new titles released every day it becomes less and less likely the good games get spotted and make money and their developers go on to make sequels.
If there were a few decent curated alternatives than I'd say this was a great idea, but when Steam corners the market so much I think releasing even more shit can only be a bad thing for gamers and developers.