While all these may be Pogba's problems, I don't believe it takes away that he's a world class player.
To a large extent, I think he's been affected by the kind of players that plays with him in midfield. We saw him at Juventus and we still see him when he plays for France, he was and is a different type of player in both teams compared to when he returns to Manchester United.
I think it's more of an environment-influenced thing for him at United because that's the only place he gives problem. Maybe the best thing is for both parties to part ways. He hasn't lived up to expectations there.
I did cover why it worked in Juventus and France
Being a world class player requires more than 10 - 20 at best - good games for a club in 6 years.
Of course, which is why I think leaving may the best option for both parties.