NT was supposed to be very tunable and modular and have multiple personalities and abstractions but it turns out it mostly is just win32-on-NT and everything else ended up being on top of win32.
It has gotten better, especially post-OneCore, but it still is very much restricted compared to Linux, BSD and Unix.
Windows NT (and VMS) were not as much multi-user server as they were more closer to mainframes (which died/are dying for their own reasons). VMS, like plan9, had concepts to allow many (theoretically) fancy server things, but were to much a created world instead of a grown world (like post-system-v). Also, while the VMS dude who was on the NT team did influence it heavily, the legacy they had to support made it almost impossible to use any of that fancy 'new' stuff back then. While it was orders of magnitude better than DOS, it feels like Windows needs to make yet another evolution like it did going from DOS to NT to get back to current times instead of patching on top of patches every time.
Windows 9x came from the single-user domain but is long dead except for compatibility stuff left over in modern Windows. Windows NT and its successors came from server space from its VMS lineage.