I do enjoy gaming, and have been known to create apps that can take advantage of rendering.What benefits would one get from Vulkan?
Another thing is the lack of SLI/Crossfire, and no real control panel for GFX cards, but I can't really put that all on Apple.
Metal is fine for iDevices, but using it for the macOS is just another way Apple is trying to reinvent the wheel, and profit at every turn of it.
How many game titles are rendering in Metal?
Who is going to port Vulkan game titles to the macOS?