When was the last time you really had to study a new concept which was totally new to you? It’s actually strange, but this is not something that happens automatically if you’re not in some kind of school. I know this is how it works for me, I really have to put serious energy in directing myself towards new things, otherwise I'm trying to work around them.
New and hard topics are actually a great way to keep developing yourself. One technique that could really help you is called the Feynman technique. At its core, it is nothing more complex than “writing out the explanation as if you had to teach the concept to someone else”. One of the powerful aspects of it is that it has to be so simple that you won’t need any prior knowledge. You’re teaching a beginner. Another part of it is that you should keep track of the things you don't get or don't know about in a notebook of some sorts.
The next time you come across a difficult topic you want to understand on a deeper level, you could try this technique to see if it makes a difference in your level of really grasping the subject.