For example, if you're on page X of a search, click on a game, and go back, guess where that takes you? Yup, page 0 baby, going to have to click next X times again (there is also only previous and next; you can't fast-jump.) There are many more examples like that, I have filed survey responses several times on issues like this.
The real goat would be if GOG Galaxy were available for Linux and integrated with Lutris/Proton so that you didn't have to worry about setup. Currently that relationship flows in the other direction, which I always found odd: Lutris integrates GOG (and Steam) games in its UI.