Just about anything GTK-based. GNOME takes minimalism too far but is undeniably polished, but Cinnamon and XFCE get much closer to a balance between good UI/UX and configurability.

Cinnamon works for me.

KDE was buggy, unreliable and annoying when I tried it--admittedly some time ago. And the fetish for naming everything with an initial letter K: kindergarten stuff.

Too much effort on making every last thing customisable and not enough on making it work?