Usable and lack of additional functionality are absolutely different things. Gnome is the most usable DE in linux, and a default for major distributions for a reason. It’s simple, it’s coherent, pretty much never breaks and just in general designed to bother you as less as possible so you can just do your work.

KDE tries to satisfy anyone with all kinds of options, but as a result most of such options are half baked and DE starts to fall apart with memory leaks and inconsistency as soon as you’re deviating from default experience enough. I do like KDE’s innovations and attempts to get as maximum performance as possible, but sad truth is that in he last 15 years I’m trying fresh KDE once in a year or two, but have to crawl back to gnome after about a week, as small but annoying problems, memory leaks or inconsistencies result in frustration.