Lol, fuck Mac. If Apple cared about gaming, they wouldn't have created Metal and collaborated on Vulkan. Fuck them. Valve went with Linux because they can change it to fit their needs. Can't do that with Apple.
Microsoft is only supported by Valve because it has large marketshare and can't be ignored, but it's clear that Valve is doing everything possible to get away from them: see Steam Deck.
In general, I agree with Steam wielding too much power and if they abused it, I'd be out. I have my gaming hours and can live without gaming no problem. They wouldn't get any more money from me as soon as they enshittified.
What would get me away from steam is an opensource gaming store with games that have no DRM and are predominantly opensource. Or another gaming store that worked on Linux and allowed playing games with my other linux buddies.
Get us that and I'm out.