Ubuntu in general I find tends to fixate on one particular thing that not many people are asking for (Unity, Mir, that "convergent phone" thing they were doing for a while, now Snaps) and let everything else stagnate until they get the thing to be almost decent, then they dump it and go chasing after the next shiny object.

I can see why it would be a bit troublesome to base a distro around. I assume that's why Mint keeps that LMDE version running as well.