Mach 2 (and thus XNU) was built on BSD 4, which was derived directly from Bell Labs UNIX V7. It has been “natively UNIX” as long as the other ancient V7 and SysV derivatives, like AIX and SunOS.
Maybe what you really mean is you don’t like UNIX and expect it to work like Linux?
Maybe what you really mean is you don’t like UNIX and expect it to work like Linux?