This is a serious topic, and unfortunately, KSP2 fails on all fronts here. And I can only talk about problems with interface, but I'm sure there's plenty more things that can be improved. Plus, if anything, the 0.1.4 made it worse.
Look at this
Let's start from the top left. The "hamburger menu". Known to exist in most mobile apps, but absent from most desktop applications, except some browsers. Alright, it's a good idea to have a button AND a hotkey (Esc), just like staging does