Watch City and this is exactly why they smash most 'smaller' teams. One of their stars sucks players in and the space created is exploited by the others. Simplistic to say but it's generally what happens and it works.
Currently the only player who can create this scenario is Martial, the rest are too slow (Mata), lacking confidence to beat men (Depay), mediocre all-round (Young) or generally shite all-round (Rooney). City have Sterling, Aguero, De Bruyne, Silva and more.
So even if Martial regularly creates space with his dribbling or attacking movement, who is really going to take advantage of it? Depay is hit or miss with his finishing, Rooney..., Young isn't great and Mata isn't having much luck either.
Van Gaal isn't helping but it is definitely partly to do with the players at the moment.