I don't know about UNIX per se, but consider Linux and MacOS progress in the last two decades. MacOS showed that it is possible for UNIX to be successful on the desktop. During the same period, Linux scaled from embedded computers and smartphones to supercomputers and servers.

In terms of innovations, I'd bet MacOS has evolved too. Although "logical partitions"-like solutions were already known for some time, Linux made it widespread through containers; io_uring allows high throughput syscall-less zero-copy data transfer and futex2 allows to implement NT synchronization semantics that are very common in game development. All that ignoring just how much the desktop changed!

The UNIX children are definitely not sitting still.

I have always wondered what the world might be like if Apple had also focused big time on developing a server version of MacOS. I am very much not a fan of Apple as a company in general but I have always liked OSX quite a bit.

Then again they would probably charge 10x as much for a 2U rackmount server where the main difference was a nice stainless steel front fascia...

They had two go's at it, A/UX and OS X Server, and ironically they do need servers for iCloud.

What does iCloud run on?

Linux. I remember someone from IS&T said Apple even forbid the usage of MacOS in their cloud platform.

macOS’s best POSIX-level innovations are probably sandbox, xpc/launchd, and libdispatch. These have been copied elsewhere as Capsicum, systemd, and libuv (TBB?), but the originals are more consistently used.

Good points all around, I stand corrected.

To some extent you are right, however as POSIX actually won the server room it will stay around for decades to come, even when it is not fully exposed as you mention.

GNU is not UNIX, though.