The KDE UI is actually a marvel of consistency, thoughtfulness, configurability, and beauty, IMO.

For your complaint, have you thought about the fact that those buttons are very useful when running in a virtualized environment (which many people, including me, frequently do)? It saves you from having to fiddle around with matching the key combinations for copy/paste you are used to on your host.

Plus, using KDE in general does not mean you have to use all it's apps. I personally use Tilix instead of Konsole most times. Just like most would probably prefer to use Firefox or some other browser instead of Konqueror.