I've used KDE quite a lot. A like it, I really do. But the amount of small issues I have with compositing and caching that build up over time, regardless of distro, until after a few months I'm plagued by flashing and compositor crashes, or menus and file managers hanging for ages...it's just untenable. There are too many small bugs in too many nooks and crannies, and with KDE's scope (and scope creep), I'm not confident they'll ever be fixed.
This has not been my experience with Kubuntu 20.04 or 22.04. I have occasionally (like maybe once every six months?) had an issue that seemed likely to be Plasma-related, and was fixed by a reboot. And there was an issue with Plasma Search where if I let it search "Recent Files", it would hang the whole UI if I did a search that (I guess) was a match for some recent files. (Worked around that by unchecking "Recent files" in the list of things that Plasma Search searches...) So I mean not 100% issue-free, but nothing like what you describe. And certainly compares quite favorably to other Linux DEs I've tried (Gnome, Mate, XFCE, LXQt).
