I like plasma as well, my main complaints with it rn are
- configuring stuff like the task bar has always been buggy, the drag/drop frustratingly won't drop stuff in the right place, I've even had to completely log out to fix being locked in the editing mode earlier this year
- settings app goes deep and it makes it harder to find simple stuff. one example for my friends is when they wanted to turn on gsync/freesync, the toggle for it on gnome is right inside of refresh rate like you'd expect
- I hate to say this because I know it's gnome/gtk's fault, but apps on gnome look much more consistent for me than apps on plasma. gtk apps don't look good, qt apps don't look good, and plasma apps do look pretty good but they're in the minority. It has been a year since I've tried ricing KDE though, so I'd accept if this has gotten better
I don't totally agree with the extensions thing, the only one I use is quake terminal so that I can have ghostty pop up (since gnome doesn't support the protocol needed for that to work natively) and I consider myself a pretty technical user. Even on plasma I like a lot of the gnome apps like nautilus for being opinionated/polished. it's been a struggle to get a good feeling environment on plasma without a lot of tinkering (which to its credit, is doable!) whereas gnome feels pretty good ootb