I LOVED KDE 3.5. Holy smokes that was a good experience for me growing up. 4 made me switch, and years later, I tried KDE 5 (last year). And eh, I really tried for two weeks. That was super annoying, and coming back to i3 just felt like finally getting air.

It was slow, things didn't work, and weird. I totally understand that people would use gnome or kde and call it a day, because it is much easier to get going with. But if you think you should invest time into your interface I would say try other things as well.

Still lots of other good things from the kde project though!