I’m looking for something simple that just works, with few crashes, few bugs and good community support. I’m moving away from Manjaro Cinnamon unstable branch to Ubuntu 20.04 and want a stable desktop environment. I only want bleeding edge software, but I want a stable foundation.
KDE 4 was pretty bad; they did a lot of work to get Plasma (5+) as good or better than most DEs, as well as being fairly lightweight.
KDE 4 was only bad because the distributions insisted on pushing out stuff that was alpha quality at best and that absolutely wasn’t ready for use. Once one of them did it, they all followed and it became a mess, despite the cries of the KDE people begging them to stop. Once the stable versions came out, it worked fine.
Overall, KDE has always been a solid desktop.
The original 4.0 release was actually a release candidate / beta release. KDE has had a bad rap since but in general has been very stable (unless you’re on wayland, there are still some bugs there).
I’ve been on Plasma Wayland for a year or more now, it’s really good. It got my 2-GPU, 6-monitor desktop setup stable as a rock vs. the fustercluck that was X11 trying to manage that.