On the contrary, I think it is completely fine to learn for the sake of learning. It doesn't preclude future action, in fact, it greatly helps it. And at young age, with probably limited responsibilities? A no-brainer the way I see it.

What would you recommend I focus on? I personally work on compilers as part of research, so that's "focus". My current broad goal is to learn all the parts of math that I feel might wind up becoming useful for applied math in the next 50-60 years. So no arithmetic geometry, yes algebraic geometry.

Biology. Bio informatics is going to be important in the next decade.