Reminds me of a talk by Hamming that went like:

"What are the important problems of your field?"

And after a week or so, "What important problems are you working on?"

And after some more time I came in one day and said, "If what you are doing is not important, and if you don't think it is going to lead to something important, why are you at Bell Labs working on it?"

Full transcript @ http://www.cs.virginia.edu/~robins/YouAndYourResearch.html

I feel like most people don't know what are the great problems in their field.

there's a lot to unpack in that statement. A good problem is good for many different reasons: it's not enough that the problem be an important one, it should also be the case that you have the techniques and knowledge to solve it; otherwise you'll be banging your head against the wall without success.

As a student, you might know that a problem is important, but you might not yet have the tools to solve it; you might not even be aware of which tools can solve it.