Dunno about KDE, they seem to be following in Gnome's footsteps these days. As for XFCE and Cinnamon, they have limited options as more and more Gnome assumptions gets baked into GTK (vanishing scrollbars anyone?). Our best bet may be XLQT, but they were lacking in manpower.
I've been a happy user of i3 for years now. I preferred KDE until 4 came out. From my perspective it was horrible and I went looking for an alternative.
I found a home in i3 and would never go back, even if KDE went back to the old desktop. When in Windows land I use virtuawin, but it doesn't touch i3.
LXQt is still going and still lacking in manpower. I used to do UX for it and still do when I have spare time but the project needs more people. If anyone wants to help, email me, jerome at leclan dot ch
I think this says more about the devs than it does the desktop environment, unless the fact that GNOME used to ship with Ubuntu skewed things.