Well, yea, that's the problem. I shouldn't have to "learn" a UI, things should be apparent and obvious.

Counterpoint: vim is very well liked for it's UI, but there's a very steep learning curve.

To your point, though, the learning process ideally ought to be seamless and linear; each new thing you can do with the application should be mostly obvious given what you already know about the UI, not force you to learn everything from scratch or do work to learn it (unless you're into that kind of thing). I don't think Discord is the worst offender of this rule, but they could make it better.