I mean, other than very old games (try running Sid Meier's Pirates under proton! it's barely playable) and user-hostile games (if the developers use anticheats

I mean, other than very old games (try running Sid Meier's Pirates under proton! it's barely playable) and user-hostile games (if the developers use anticheats which block Linux on purpose, that's not really Linux's fault) we are at least 95% of the way there. Sure, there will always be someone who will complain that "Valorant doesn't run on Linux" but the overwhelming majority of games do.