the main issue with Pogba is hes at his best when he plays it simple and works hard, like he did during the WC for France. due to his ego/flamboyant personality though he wants to do skills and flicks for the highlights which is a waste of time in a team like United. hes an idiot for going back there during the rebuild
iirc Mourinho said something along the lines of 'he cant play like this for a full season' when commenting on Pogbas world cup performances and hes right, Pogba won't sacrifice himself for the team
He's at his best when he has great players making runs behind upfront because his main quality is long balls. That's why he mostly sucks at MU, nobody good upfront running behind the lines (when they did, he provided multiple assists).
He makes amazing long ball assists. He also has to play low on the pitch like he did for France to maximize his long balls. Zidane knows that I think. When he does that, he's one of the most valuable midfields in the world. It could definitely work a lot better in Madrid than in MU.
He brought half of France WC with his long balls and assists. That's what he does. Nobody outside Deschamps understands the player he is, even not himself I think.
He can make runs himself and score goals, but if he does, you're losing the best part of him, which is long balls quality. That's why Deschamps made him play so low on the field and got so much from him.
Work rate is an illusion, you just have to provide him targets for his long balls, which MU rarely does.