For starters, I can respond to this line: I haven't gamed on a Microsoft product since I switched to Valve's Proton. That's a good thing, and Valve putting that leverage there really opens the door for other manufacturers. Better yet, it kicks both Microsoft and Sony in the pants and asks them to come up with a better reason to exist than "API exclusivity". That's badass, in my book.
As for Sony, I don't think it's hard to see that they're struggling here. The end of the PS4's lifecycle was a bit of a mess, and resulted in Sony changing their attitude for a lot of things like crossplay and publishing to PC. The featureset for the PS5 is almost comically gimmecky, the games cost too much, and without backwards-compatibility the game library would be almost empty. It distinctly feels like Sony's strategy of using exclusives to bolster cross-platform releases isn't working anymore.
My point here isn't to bash Sony, but to highlight that they have professional agency and have repeatedly made poor choices in software and hardware. It's fine if you want to zoom-in on the decidedly small arena of "Sony vs Microsoft", but it's hard to look at their fight and say that it's not Sony's fault.