You've just answered the problem, Bruce.I think he is a decent player made to look bad by hoofball football and midfield players who lack energy and craft.
Grealish tries but the worse the other midfielders around him play the more he tries to do resulting in him going deeper when he should be playing at the top of the pitch and where his game is most suited for.
All this while Bruce & Co stand on the touchline wondering what's going on and unable to change the obvious.