To me Mac has an issue that is very clear: he is great at diagnosing the defense pre snap, he'll get the team into the right play, he'll set the protection, he'll understand the front, the scheme, if there's pressure coming, he has a great grasp at the line of scrimmage. But if the ball is snapped and that picture he had in his head pre snap isn't confirmed, or if a receiver loses/doesn't get the leverage he expected, or a lineman is beaten, he's not a quick enough processor to go to plan B on the jump and maintain the same level of execution. Sometimes people seem to conflate these things, but diagnosing the defense and knowing your plan of attack is a different skill from being able to read/react to movement in real time and make decisions. If the ball comes out, the intended receiver wins and everything goes to plan, he'll hit his back foot and deliver the pass with confidence, if he has to move a little off his spot or go to his second read he sputters. He has a tendency to throw while drifting back/falling away, he starts getting on his toes, the ball just doesn't come out the same. And he doesn't have the arm that allows him to challenge windows if he's a tad late. That's where he gets in trouble. But if things are humming schematically, he can ball.