The UI elements could possibly use some scaling down, but yeah, my only real gripe with the UI is just the lack of an overlay TBH. Everything else I can handle.
It's developed for both so it does have to be console friendly. That said, you can map out and navigate menus fairly quickly like you would expect. It might look like it, but it certainly has far more care put into the UI than most games that were developed for consoles in mind and thrown on the PC with little thought. It's clear that it was developed for PC first.
Why they don't have an overlay is a mystery to me though. Pretty much a staple in all previous Diablo entries and basically every other ARPG on the market lol.