Linux used to be a pretty good UNIX, I'm not sure what it is now.

Linux has become Linux, it's own thing that as often as not says "yeah, that old Unix stuff is fine for you boomers and other fossils...we're going to be over here doing our own thing". Which is probably fine, I guess, because all the old Unix versions did the same thing to some extent and the computing world had changed over a dozen times since Unix showed up. Unless you were on one of the minimally massaged System V reference ports, going from one vendor to another was anything between "lots of annoying differences that make life less fun than it could be" to "WTF said this was Unix and why did you make me touch it?". Ultrix, SCO and UTek (among many others) weren't awful. Solaris and HP/UX had some vendor-only things that were hard to replicate. AIX made you question your life choices, especially if you wandered off into one of the mainframe versions; you had clearly angered the gods.

There used to be Windows, Unix, and everything else. Now there's Windows, Linux, and everything else, with Unix (BSD mostly) being part of everything else. Times change, shit happens, and there's only so much that impotently shaking your fist at the unjust universe will fix.