I agree with this, you can't just beat the Sicilian "with the opening principles" am I right? Opening principles take 5 minutes to learn and in open situations even a baby could apply them, if you want to learn openings as a lower rated player there is no reason you shouldn't!
You can't just beat any openings with opening principles. That's why the game usually also features a middlegame and potentially an endgame.
When people say 'don't study openings' it does not mean that you shouldn't study the middlegames. So, don't learn the first 20 moves of a line in the Dragon, but do study positions with opposite castling. Don't study 20 lines in the Shvesnikov, but do study positions with a backwards pawn and/or with strong squares.
I try to learn openings