I think it's time people stop making excuses for Marcus.
It doesn't matter if he is playing PG or SG. If he is playing of the ball or if he has the ball in his hands. If he had injuries or not.
He has to make better offensive decisions. And, if he makes the right decision, than he has to execute that decision better than he does right now.
He is taking three pointers like he is Klay, Ray, Steph or Kyle. The problem is, he is shooting them worse than Starbury. A good offensive player knows exactly what his strengths and his weaknesses are. Only take the three when wide open, and when the pass comes from in front of you. If not, than turn that shot down, until your shooting improves.