[puelocesar]

It’s not the “walled garden” that’s preventing Valve to write Proton for Mac, it’s the lack of Vulcan support. Apple pushed to its own Metal framework when they deprecated OpenGl, which is probably great for performance, but outright denying support for Vulkan was a killer blow for games.

[jillesvangurp]

Which they could choose to fix but didn't because they are treating it as a walled garden. Which is the same reason they removed the OpenGL support and declined to update/modernize that implementation. As reverse engineering efforts for asahi linux have shown, implementing Vulkan is perfectly possible and apparently runs with pretty decent performance. And as Apple's own efforts with the game porting kit show, supporting DirectX is also not an impossibility and there are some examples of ported games in the Apple store.

Apple religiously defends its walled gardens. Stuff like this is the exact symptom. They don't allow third parties to "fix" this either. They don't really document their own hardware and treat it as a control point. They also don't support independent efforts to port other operating systems on mac hardware.