Never settle for the “what”. If you can't get to “your why”, at least get to someone's “why”. Whats are cheap and transient, Whys are enlightening and transferrable.
Despite my total comfort with promoting polymathism, it creates a few dilemmas. Paramount among them is exactly how far to push oneself in a particular pursuit. How do you know when you've mastered “enough” of something? When does the 80/20 rule kick in?
My personal guideline is to get to “your why”.
Let's say you're learning about the symphonies of Beethoven. Don't settle for regurgitating which of the nine symphonies are “famous”. Get enough of the fundamentals of music and music history under your belt that you could decide for yourself which ones should be historically important.
What if you're learning about something more concrete like the electronics of amplifier design? It shouldn't be sufficient to decide that you look down on Class D Switching Amplifiers as acoustically inferior. You should push yourself to be able to give a well-reasoned argument to another expert on why you've adopted that bias.