He added: "The reason Wayne Rooney has scored so many goals for Manchester United and at international level is because he got good service.
Now he gets the ball in the middle of the pitch and it’s difficult to score the goals.
"If you get the ball out wide with wingers and play more aggressive there is more chance of scoring goals.
"Now it's normal for Manchester United to keep possession, pass, pass, backpass. There is no attacking."
The lack of wingers at the club is a cause for concern and an area which needs to be improved, according to Kanchelskis.
This is a different system and now it is cautious. We played 4-4-2 with wingers – myself, Ryan Giggs, Ronaldo, David Beckham.
"There were so many good wingers. But Van Gaal doesn't want to play with wingers."
United return to Premier League action this weekend as they face Chelsea at Stamford Bridge.
Read the full 888sport.com interview with Kanchelskis here, including why he thinks United are to blame for Rooney's slump.