>It's one thing to "know" how to balance a binary tree because you've read up on and practiced the most common challenges - it's something else entirely to actually think through and understand a problem, then come up with a solution.

There are too many things to know in the world in order to be able to know them all as deeply as we wish. For the things that we can get away with knowing the most common aspects of, time might be better spent elsewhere than to learn more about that thing.