Whilst I agree with you about the two man midfield, the rest is nonsense which constantly gets spouted. If you take Yaya out, we wouldn't play with 10 or wouldn't have Fernando etc as the long term replacement. We miss him if he misses a game, just as we miss Silva or Aguero, but if he hadn't joined or if he was to leave, we'd find a quality central midfielder to replace him, just as we'd replace Aguero. Pogba is obviously seen as an option, but there will be others.
To claim that we only won stuff because he was playing is a disservice to the rest of the squad. You could just as easily claim we'd have won more if he'd been replaced by a quality player who gave us 90 minutes each week, rather than a few moments of brilliance few others could do. Both are hypothetical arguments which no one can prove.