When I first tried KDE, it was during the Plasma 4 days and ran as slow as molasses (not to mention the constant crashing leaving me with a black screen). Friends convinced me about a decade later to try Plasma 5: it is no longer a slow, buggy experience, they claimed. Well, I set up Debian 10 with Plasma 5 and changing the default KDE cursor to the black Adwaita cursor already didn't work! Depending on which window my cursor was hovering, it would change between my custom cursor and the default KDE cursor. This was after applying settings and restarting KDE. And forget any modifications you make if you use SDDM, it always seems to use defaults.
The comprehensiveness of Adwaita as an icon set and the relative stability of GNOME is what keeps me on GNOME. If I had to ditch GNOME, I would probably choose MATE or Xfce next. I've been fooled too many times by KDE evangelists claiming everything's fine and rosey nowadays and we are totally no longer in the Plasma 4 days.