Steam clearly shows a badge showing if it runs on Linux. You can filter out stuff that won’t run.

Just filter out: Fortnite, Roblox, GTA Online, Call of Duty, Destiny, Valorant, PUBG, etc...

It isn't a short list of AAA games that don't run on SteamOS.

There's no game worth installing a rootkit for. The market is far more diverse and interesting than the handful of popular AAA titles , most of which are just shooters

There is a certain group of gamers who care about all of those games, but there is a not insignificant group who doesn't at all. So while it's not a non issue, it's not a show stopper that you can't play online shooter games. And that really is the only genre of game that won't work. Everything else has been flawless on linux.