It often seems to me that I haven't learned much lately, and then I see something which makes me think "I would not have even have understood what this is about

It often seems to me that I haven't learned much lately, and then I see something which makes me think "I would not have even have understood what this is about two years ago." What people need to do well and grow in their vocation and avocations is to understand the field, and understanding is not just a matter of knowing a collection of immediately-relevant facts. Learning (more than just knowing) this math and other concepts is the sort of thing that leads to understanding; for one thing, it provides an explanation and justification for the pragmatic facts and links them as a cohesive whole.