#1 Manchester United's forwards do not fit into Mourinho's defensive football system

Manchester United has spent a hefty amount in the last few transfer windows to sign quality forwards. For instance, United signed star winger Alexis Sanchez in a swap deal from Arsenal.
Romelu Lukaku also joined Manchester United last season from Everton for £75 million, and he is one of the best strikers in the world at the moment. Anthony Martial is also another notable Man Utd striker known for his incredible pace and dribbling ability, and there are homegrown talented Manchester United forward players like Marcus Rashford and Jesse Lingard on the roster as well.
However, despite having such an awe-inspiring forward line-up, the club's total number of goals is not impressive. In fact, Premier League rivals like Liverpool, Arsenal and Manchester City scored more Premier League goals than Manchester United last season.
Mourinho's defensive style is one major reason for the below par performance of the Manchester United attack. Therefore Mourinho needs to adopt an attacking approach, and he needs to provide players more freedom on the pitch.