Actually, they kinda do take responsibility for mac gaming. They helped develop https://github.com/KhronosGroup/MoltenVK which basically runs Vulkan on Metal. The Linux version uses Vulkan, so in theory it shouldn't be too hard to port, they just didn't.
That's funny because my son compared CS2 on my MacBook Pro vs his RTX 3060 PC build we put together last winter and he said how much more responsive the game felt on the Mac.
That it works is one thing. That it always works as expected is another. Apple doesn't want to take responsibility for that, and neither does Valve, when there's not enough paying customers on that platform. It is what it is. Now the Proton layer is one thing, because Valve is selling Steam Decks. They will want that to become a big thing. They'll go back to selling Steam Boxes (the living room console thing).
They ship an outdated and unreliable implementation 😅 There are things that use it, but my understanding is you couldn't use it in the same way you can on other platforms.
Steve Jobs quite openly hated the idea of anyone gaming on a Mac because he felt like it made their products seem more childish or something. It seems like either nobody at Apple has managed to dig that particular brainworm out yet or have just decided that printing iPhone money makes all other concerns irrelevant.