Obviously, just because you study something intently doesn't mean you understand it
Learning other stuff in the process?
Gaining a better idea of what the thing you study entails, even if you don't understand it fully yet?
What I mean is, you can study something even if you know that you won't understand it at the end of your studies. There's even stuff that you can have a full career in and still not understand completely, like Quantum Mechanics.
It's not a guarantee that by studying something you'll understand it, but learning more about it can be valuable in itself.
For example I can study some X technique in a language, e.g Monads, and know when to apply it and what it does, and be quite productive with it, even if I don't yet understand it (or never get to understanding type theory).