He was a decent player and still is, he is not a great player. He is a leader, a team player, keeps it simple, plays with discipline and makes sure he gets the basics of playing midfield right. He is limited but he has worked incredibly hard on improving his all round game and works incredibly hard everything he plays.
Pogba is the opposite of this in every way, a supremely gifted footballer, who has been living off his highlight reels for far too long. He is 28, he is not going to change his ways at Utd, Jose got the blame for him being shit, Ole came in and he played really well for a bit. Now he's gone to the dogs again and it's all the coaches fault that he is isn't playing well, "they can't coach", "they aren't using him correctly", "he's played out of position", "he doesn't have the right players around him".
There's only one reason he hasn't worked out at Utd and that is him.