A lot of players receive unfair criticism it's not just him, especially at big clubs. The better a player is the higher the expectations get and due to his price-tag and skills, his issues of not performing consistently for us will give you a lot of bollocks. It's obviously annoying, but one thing that kinda justifies some big criticisms is the actions of his agent etc. Those things just paints a picture for everyone that this player doesn't want to be a Man Utd player, and if you don't play or perform to disprove it, then obviously you'll receive some harsh criticism. Obviously if you're a good guy and look for things in Pogba you wont find much wrong with anything he does, but I think it's good to differentiate between those just making judgement for the feck of it, and those who generally just wants whats best for the club. Sometimes if you have a good player, it can be to the detriment of a team. Only a few players are good enough to go beyond that, like Messi and Ronaldo. They are just untouchable, if they don't function you don't change them you change the team.. and Pogba just haven't proved himself to be one of those guys.
All players needs to work on gaining the fans trust after letting their agent attack the manager of the club. It's almost unheard of. I think it's easy for Pogba, he only needs to gain fitness, settle down and sign a new contract, then shut up and play. It's really easy if that's what he wants. If he doesn't, then a lot of the critique has sort of been warranted hasn't it.