Sancho isn't as good as he's made out to be. He isn't explosive, isn't fast and doesn't have a great shot (like a Coutinho). What he does have is the ability to play at lots of angles, good combination play (1-2s etc), he makes runs in behind- he is a creative wide player.
This is the type of thing Sancho can offer. Runs in behind and beats his man 1v1. Then he sees the pass and makes it at a tight angles, even in the box. Good interplay in and around the box.
This is another small example of what Sancho's good at. He's willing to run in behind which helps create things- opens up space.
Not being explosive is what caps his potential however. All of the elite wingers are explosive- it helps them get away from their man to: make a pass, shoot, draw a foul etc. Mané, Messi, Hazard, Neymar, Mbappe etc. Sancho isn't explosive so he's limited in a sense.
This is what I mean when I say he hasn't got the same speed when moving the ball that others do. Look how much space he has to come inside. You know Hazard, Neymar, Mané etc are attacking that space with speed and causing all types of issues.
Look at this from Mbappe, he's moving the ball slowly and nothing is really on. Suddenly he explodes past 2 and Neymar has a simple tap-in to give his side a crucial away goal. Explosion.
Sancho is a creative winger- not many around nowadays because people want goals from their wingers and that creative role is given to other positions (FBs, 8s). You want a balance of players he can combine with and players that will run in behind to give him space to operate in
That's why Sancho and Hakimi work well together. Sancho has Hakimi creating width and running in behind in the areas that he operates in- Hakimi makes the pitch bigger for him.
He can certainly be a useful player but I don't think he's a potential Ballon D'or winning player which is what he's made out to be. We're seeing 80m+ fees being discussed but when you think about who he's seriously linked with it's just been United and Chelsea.
Chelsea look like they've chosen other options now too. Real Madrid- No, Barcelona- No, Liverpool- No, Arsenal-No, Bayern- No -> a 'generational winger' is only really wanted by Manchester United. Interesting. Also have to remember that Pep let him go.
Sancho at United would be slightly awkward because AWB isn't suited to overlapping. Sancho needs a RB/RWB that will overlap and act as an outlet for him. With AWB, United need a RW that will provide width- Sancho's more suited to drifting.
Then there's things like coming back to football overweight which puts doubt in your mind.
So what Sancho needs is players that he can link-up with but also players that will make the pitch bigger for him (they need to run in behind/overlap). You need a fast winger on the opposite flank of Sancho too.
He needs space because intricate play is hard to do when zones you're operating in are congested. That's why lots of these technical, creative types are rarer in football today- not enough time and space to play their game effectively.