He would be perfect for United, but for City he is too similar to what they already have. We have/had plenty of great runners and counter attack players, but we lack those to unlock tight defenses. Yesterday he was on a break, and I couldn't help think that if it was Sane or Rashford instead, he would have broke through. He isn't fast enough to exploit spaces in behind, and none of their attackers are. Even Sterling lacks top speed. They are great at close control in and around the box, but PSG could ward off pretty much everything because there were nobody that could attack them from deep. That allowed PSG to sit high when in possession without risking anyone running in behind. When City were in control, they could just stick close to the players and crowd them out because they knew they could always get one back on them.
City are the opposite of United in attack - great at close control, but they ultimately have too many similar players that all want to do the same things. Corner of the 18 yard box, flick left, flick right, turn inside, play it short, and shuffle. Nobody threatens on the outside. Grealish, Bernardo, Sterling, Mahrez are very similar, and Foden and KDB are not that different.