Ah, now there we're in agreement. The state (and future) of OpenGL on the Mac had been obvious for at least two major OS releases. Frontier could (and should, IMHO) have started re-tooling for Metal. They'd already coded (or were coding) for two different graphics libraries apart from OpenGL, so another one wouldn't have been impossible.
But that's a whole other sack of badgers.
[Edit: originally said three different graphics libraries, but Xbox is probably using something akin to DirectX, so basically the same as PC]
Now, now, the reasons for the demise of the macOS client is immaterial, I'm just using it to illustrate the point that the money put in for that version was a risk that did not pay off.