MacOS is only as good as its hardware integration. Lifting and shifting MacOS UX to another system would only be skin deep. Much of the simplicity (and ire to many technical users) of MacOS is because its deep vertical integration.

MacOS is Unix -- a BSD-derived Unix operating system called "Darwin" underlies the user interface.

https://en.wikipedia.org/wiki/Darwin_(operating_system)

macOS is unix...

And he seems to not want macOS type design. Unless you mean System 8/9.

Modern macOS design is reasonably consistent but with fewer visual cues - still a step above Windows post-7. And yes, I meant the bezels and skeuomorphism of earlier design - exemplified by Windows 9x-2k and System 8/9, while NeXT and IRIX also deserve a shout.

That was the plan for Étoilé but it didn't get traction for some reason.

There are: ravynOS and helloSystem.