Strictly speaking, only the kernel is unified in Linux. The "rest" depends on what the "people from a specific distribution" will do. By "the rest" can be understood:
- windows and GUI,
- multimedia (audio, video, imaging),
- support for I/O devices other than the standard keyboard and mouse.
You could probably find more of it. Therefore, Linux on workstations (desktop) is basically a substitute for OS, unlike servers. In this respect, there are no charismatic programmers (like LT) who would force a specific solution (as is the case with the kernel). Therefore, in Linux, an ordinary user (and a "non-system programmer") is doomed to deal with a mess of many incompatible and/or mutually exclusive solutions, wasting time and frayed nerves.