Our current run is built upon being a team. We've a great double pivot that is complementing each other well in Matic / Scott / Fred (one being left out in any given game) who give that base for Bruno and the forwards to build off. They link the defence to attack, move the ball quickly and provide solidity for the defence.
Bring Pogba in, and you're back to showboating, taking too many touches in midfield, not tracking back. Now, obviously he's capable of moments of pure genius. But would the team benefit, for sure? Possibly, but I wouldn't say it's nailed down.
When we've a tough game that needs fighters, he'd more likely disappear in my opinion, as we've seen in the past. His character is that, if the chips are down, flight. Look at the history with us. Not getting his game at United? Leave. Come back, things aren't going well, uses 2 mouthpieces to try and get a way out. In games where we're struggling, and it's a dogfight, can probably count on 1 hand the number of times he's been in the fight and helped.