it does matter who the QB is. If th coverage is tight, the QB needs to put the ball into a small window and throw it hard. They also need to deliver the ball quickly before the WR completes the route.
Also, I have seen Grant and other WRs get separation.
If the standard plays don't work try something else. Pick routes, screens, and use the play to help create space.
It wasn't just getting separation. Did you not watch the game? Laviano's passes were SO BAD. He threw short, at the feet of the receivers or completely over their heads. I counted at least seven times when a catch would have easily been made if the throw was accurate. CL just didn't make the throws he needed on those seven occasions.