I thought the UI isn't that bad until I tried Gravit Designer. I don't know if it's comparable to Inkscape in terms of features, but to me as a more occasional user it's a vast difference in usability(even considering the compulsory online account with Gravit). Maybe more proficient users would feel different but in Inkscape there are so many buttons and switches visible at all times that I constantly have to look for the right one.

But again, that's just me as someone using it every couple of months; in general I always manage to get the stuff done in Inkscape and it seems pretty solid behind the UI.