I can only speak from my experience but blitz worked for me. I would make occasional, furtive attempts to learn but nothing ever worked. Then one day I started playing a single five minute lichess game with coffee in the morning at work. And when I would make a mistake, I would do a takeback to see what I did wrong and how I should have played it. Sometimes I would play the puzzles.

Doing this and nothing else, I went up about 100 points a year for five years, from 1200 to 1700. (And then I stopped but I also could tell that I would have to start approaching it differently to go further.)