I get that he hasn't been given a prolonged spell. But a fair few of our players have not had that. Kane, Mason for example. They impress without needing a prolonged spell. So why can't our £16mil Brazil international do the same?
He will not get a prolonged spell in the side if he continues to look shit in the games he does play.
I think a few of us that still support the Spurs player named Paulinho have answered the question why he is not impressive in the few games he've had several times:
1. Terrible team setups for him. He is the kind of player that thrives in a good team, with players able to take advantage of his superb movement by passing the ball or exploiting space.
2. Rock bottom confidence.
3. Harassment from the stands.
The first point requires a bit of understanding the game. The other two are blatantly obvious through example from the world of football every season.
So, then, to your question about why others with limited time on the pitch can impress:
1. Different players have different needs from their surroundings. Kane, for example, has a playstyle where he looks to get on the ball, rather than that of making the most creative run, and is making things happen through his involvement. He is also used to playing with and against lower quality teams. Suits better in the cup setups than does Paulinho.
2. Not rock bottom confidence.
3. Support, rather than harassment, from the stands.
4. Your perception of what makes for an impressive display is affected by your expectations. What is deemed as an impressive display by Mason, would probably be seen as another unimpressive game if it was performed by Paulinho.