KDE Plasma 5 is actually at a great state right now. It works well and you can customize it to me whatever kind of desktop you like. Canonical could have made it into whatever they wanted it to be.

It's built on top of a Qt, that works everywhere instead of GTK that just focuses on being there for GNOME. In addition to that canonical has already been using Qt for the past few years and could have just continued on with it. Alas, the decision has been made and they're not going to be changing their mind anytime soon.