The inability to remove files from your drive is quite a lot.

And DRM-free games on steam are not that many, most have at least something that closes the game if you don’t have steam running and I’m a bit sick of having to use goldberg every time I want to use a game without starting steam.

Of course GoG has a lot of (pretty bad) issues, but it’s like comparing a cold to a cancer, it’s absurd. Steam is actively destroying both game ownership (by allowing more and more DRM methods, now with games telling you to accept 5 different terms of use all indicating that you are heavily tracked while using the game for example) and game quality by encouraging the shittiest game, with a main page being completely unusable if you don’t filter out keywords such as nudity, nsfw, mmorpg, etc. GoG isn’t to that extent. Other things exist and if for example Itch had a better interface and search system it would unequivocally be the best game platform I am aware of as of now, sure. But trying to say that GoG and steam are the same (or that GoG is worse) is really not possible to do unless you actually don’t give a shit about games.