I'm not even really convinced that Marcus taking a lot of shots hurts the team.
The opponent often defends him as if he is a good shooter even though he's obviously not. See Matt Moore's work on this for supporting evidence.
I think that's a product of the fact that he occasionally gets hot, and the fact that he shoots with confidence as if he were a good shooter.
In the playoffs, if an opponent gameplans for him and actually has their defenders leave him wide open -- like teams sometimes do to Draymond Green in the playoffs -- he will need to either hit his shots (like Draymond), or adjust.
But in the regular season, if his shooting is spacing the floor by drawing defenders, it's not even that big a deal if the shots don't go in very often, as long as he's not looking off open teammates or shooting super early in the shot clock, which I don't see him do that often.