KDE is my favorite DE by far and it is very much the most advanced environment I know. The integration is the best and the ability to tweak everything is great.

Personally I use i3 90% of the time and use many KDE applications. KDiff, Dolphin and Gwenview are my go to for me, well that and ranger the console file manager.

KDE always felt quite sloppy to me, too much going on, weird borders and decorations, screwy inconsistent padding etc.

Looks almost nice, but feels like spacing and font size is wrong on some places. Maybe I'm just used to win10...

Definitely, there’s a lot to improve, and it certainly isn’t perfect – but it’s not a desktop that you’d compare to Windows 95 or CDE.

elementaryOS ever more so. Although, it is a bit of a clone of MacOSX which may be a turn off for some but still is quite user friendly.

I installed it for my family members ( not at all knowledgeable people in terms of computers etc ) and they all have gotten along with it very well.

KDE Plasma recently added a new unified theming system, and there is now a theme to make KDE Plasma look and work exactly like macOS with that (with menus in top bar, dock, etc)

But yes, elementary does the "good defaults are impirtant" very well.