Yeah, but you still didn't address my point:
How do you narrow down the many variations to the exact variation you are going to choose to play?
For instance, if you wanted to learn how to play the White side of the Slav or Semi-Slav, how would you wade through the tons of material on that opening and find something to focus on?
I think there are over 400 hours of videos on just that one opening alone...
Lets say your goal was to develop an opening repertoire that was comprehensive and could get your through to the middle game in any tournament you played.
This task seems somewhat overwhelming. Seems that if you rely on some of the chess.com videos, that would take too long and be inefficient. You'd also be forced to be spoon-fed whatever lines are picked out for you.
If you go through a database, you will just find an overwhelming number of variations, and you won't be sure what the plans are, or what the ideas are behind some of the moves. Also will be hard to narrow down these choices, there are simply too many.
So that would leave just buying a book, but that also has its shortcomings as well. Again, you're just stuck playing whatever lines the book chooses for you, and you can't buy a book on every single opening you're interested in.
So in general, how would you go about creating this opening repertoire?