The App Store itself is now multiple stores. Some games you can buy outright, and others you have to subscribe to Apple Arcade to play.
I can mostly use Steam. Pretty much the only reason I also use other game stores is because of free game giveaways (Amazon Prime, Epic, GOG), or cheap bundles (humble, itch.io). 90%+ of the games I launch from other clients I could have purchased from Steam instead. For all the complaints about exclusivity on stores like Epic, in has less than a dozen exclusives that most gamers would have heard of, and about 40 in total. That's a drop in the bucket compared to the the number of quality games available on Steam.
What drives me crazy is that I have a lot of games that used to work on older Macs or iPads that no longer work on the newer OS releases. I have very few PC games that are incompatible with the newest version of Windows. But the nice thing is that if I bought a Steam game to play on a Mac, and new versions of MacOS stop working with it, I can still use the same purchase to play the PC version.
For PC gaming, you can stick exclusively to Steam and you'll have a better gaming library than you'd have on any Apple system (unless you only like playing Minecraft without mods, I guess).