OK, you've clearly seen more of him than I have, but to me he seems an extremely raw player that is often not in harmony with the rest of the team on the pitch. If Barcelona were an orchestra he'd be off tune. He's just not in the same flow and rhythm as the rest of the team. When he gets the ball, the attacking pattern breaks down and he just does his own instinctive move. That to me doesn't scream generational talent, that to me screams capricious virtuoso about to sit on the bench. Add going on strike at Dortmund demanding a transfer, showing up late for training because he was playing Fortnite all night, not being professional about his diet, fitness etc. and you've got a flawed professional, albeit a talented one.
Look Barca, are not necessarily a paragon of stability - plenty of players have failed there and had a good career elsewhere. But don't think United should look at him. He could have succeeded at Fergie's United, no chance in hell he does so in this current setup.