Both things can be true.
McCord is a stud, and Marvin Harrison Jr made him look good.
There is a video upthread which has virtually every pass McCord threw last season. He's a very good quarterback.
Some of his misfires were still caught because Harrison is just that good. His adjustments to the ball are amazing.
That said, maybe McCord throws for a couple hundred fewer yards and a few less touchdowns if he has merely "good" receivers instead of a "great" one?
McCord is going to be the best throwing QB we've had at least since Nassib, and maybe forever.