ProtonDB rates 28% of the top 1000 games as platinum ("runs perfectly out of the box"). The rest either need some tweaks, have some issues, or just don't work. My assumption is that most gamers don't care too much tweak with their games, so I wouldn't put that much weight on the gold category. And when it comes to silver and below, that can be pretty nasty.
And when looking at the top 20 most played games on Steam, there's some pretty big titles missing. PUBG (5th most played) is borked, CoD MWII (6th) is borked, Destiny 2 (9th) is borked, Rainbow Six Siege (10th) is borked, FIFA 23 (11th) is borked, NARAKA: BLADEPOINT (13th) is silver, Rust (14th) is bronze and Dead by Daylight (20th) is bronze. So when it comes to "most players", there's definitely a lot of gaps too.
I have a Steam Deck and I can have pretty good gaming experiences on it. Surprisingly even. But it's definitely not perfect, and one of the reasons why I can feel pretty confident in owning a Steam Deck is that I still have a Windows-based gaming PC that I can fall back on.
Don't know about the rest, but destiny 2 works fine on linux...you will just get banned by anti-cheat. The only reason you can't play Destiny 2 on linux is because Bungie won't allow it. It even has working anti-cheat.
