KDE is now my favorite desktop

We now live in a world where KDE looks nicer, more professional, and more consistent than the latest macOS. I don't know how that happened, and KDE isn't even particularly nice looking, but here we are.

For many years now KDE has focused on polish, bug fixing and "nice-to-have" improvements rather than major redesigns, and it paid off.

Major changes aren't even _desirable_ in UI. People kind of emotionally enjoy novelty, however when it actually comes to using a computer consistency is superior to absolute excellence. Figuring out where settings and buttons are just because you ran software updates is a total waste of time on both ends; it wastes the user's time, and was a waste of time to develop. Maybe I'll switch from gnome to KDE this weekend, this looks promising.

This is an opinion stated as fact. Not every user is the same. That's why there are loads of apps with UIs that have different user modes, for power users, etc. KDE is most suitable for power users of Linux desktops, probably who use it as their daily driver. If you aren't in that category, you may not like it or may find it to be not worth the time investment in.

Not every user is the same, but it's absolutely valid to discuss whether broadly for most users constantly-churning UI is a net positive or net negative. I think your case, ie customizable UIs, is something of an edge case, and I do agree with you that expert versions of simple UIs can be a really positive move.