I have never made a move from my database without knowing the reason for it. I was always taught that learning openings by rote without knowing the ideas behind it was a recipe for disaster.
I play the QG as white. In a tournament game a while back I was confronted by 1. d4 d5 2. Nf3 as black. I had never seen this before so I decided to play 2. ... c5. This is similar but not identical to a QG. Because I not only knew the moves for the QG but also the ideas and patterns I was able to play well in this similar but not identical system. Whereas if I just knew the moves then I probably would have struggled.
A saying comes to mind "Learn from others' mistakes, you don't have time to make them all yourself."