It's true that no one should judge holding midfielders in the current game for their goals or assists. In fact, in most systems these days the fullbacks are far more likely to get into attacking positions than them. In the current Chelsea or Spurs team people would be mad to ask Kante, Matic, Dembele or Wanyama about their goal and assist output. In Madrid similarly, it's more common to see Marcelo in an offensive position than Modric, who is more often the player who pass to Marcelo. It seems to me that the 'defensive unit' is more often the central defenders and central midfielders these days rather than the fullbacks who are instead expected to play as wingers when in possession with the holding midfielder covering them.
With Pogba, I'm not sure he is best utilized as a CM in this more recent system many teams use today. If so he will need to improve his positioning, defensive awareness etc etc imo. He is nowhere near most of the CM's today in providing balance to the team, controlling the tempo of the game, stability or a platform for the attackers. He is far better if allowed to be allowed to express himself offensively for me, and this is still possible coming from deep in a system where he is allowed to drop deep and be part of the buildup play, but also break forward at will. If, for example he played in a 4-3-3 there would be other players behind/beside him allowing him the freedom to play.
But if he does occupy such a role he will also be judged on his offensive output since he will be free to break forward with runs from deep into the box as well as occupy dangerous positions. I think this role will suit him best, but this role doesn't really exist in a 4-2-3-1 since the three attackers behind the striker will also occupy similar spaces. If he is to be used as one of the front three, he will definitely be judged on his goals and assists since he will then basically play as a forward, who can track back, but is allowed freedom in the attacking third. I'm curious of how Mourinho will use him next season.