His problem is that he's a legend in his own mind.
Pogba thinks he's just fecking great at football. To be fair, he's pretty fecking good but his mindset is such that he will never apply himself. As a result he will never fulfil his potential.
Pogba is at his best when he has players making runs behind between the lines, because his biggest asset is his long balls and thats why France benifited so much.
For Pogba to be successsfull he has to play in a low block, like he did for France, to maximize his long range passing, playing it simple, something that Mourinho tried to get him to do at the same time develop his positional sense, and also get Martial, Lukaku and Rashford to make those runs.
Deschamps quote "Paul Pogba can do everything but he cannot do everything all alone,"
Yes Pogba is able to make runs himself and score goals, but if he does, you're losing the best part of him, which is his long balls quality. That's why Deschamps made him play so low on the field and got so much from him.
You just have to provide him targets for his long balls, and he will shine. he actually reminds me of Xabi Alonso with his passing, who was no speed merchant or a player with high work rate, but was able to develop his positional side of the game, to allow him to make interceptions and continue to recycle the ball, helping his team to benefit from his strengths, remember Xabi came from Real Sociedad to Liverpool and the time he spent playing in the premier league benifited him so much, that Real Madrid, Bayern and Spain, were all able to take advantage of his development in his game.
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, if he did or does, things would be alot more different.