Super cool people maintain and expand things like KDE 3 and Gnome 2 (Trinity, Mate)! However personally I don't feel the need anymore. Gnome 3 and KDE 4 are both quite usable. Which is a stark contrast from when Gnome 3 and KDE 4 came out. They were both nothing more then glorified beta's. The first release of Gnome 3 was basically like the first Windows 10 release with the Metro UI; Totally unusable. Not that surpri…
It seems somewhere around the late 2000s both projects got very nice and usable desktop environments, couldn't figure out how to "evolve" next (because apparently software just can't not evolve) and started throwing shit at the wall to see what sticks. And unsurprisingly, a lot of it did stick.
To its credit, KDE 5 does seem to try to clean up the mess a bit though in that over the years it is the only between the two that doesn't compulsively make me want to remove it from any Linux machine i get my hands on (and can remove stuff :-P).
Sadly XFCE seems to be heading down the same way.