KDE's changed its look, but more importantly, it's not set in stone: it's entirely possible to change its settings and theme. It's the most configurable DE out there.

I really wonder sometimes why distros don't use it more, and make their own custom themes for it, instead of just leaving it at the default. It wouldn't take that much work to make themes to make it look almost like anything you want. Or you could even make a different version of Plasma which emulates some other OS/DE if you needed to, leaving all the underpinnings intact.