I was a big Mac supporter, but he's still a mess mechanically, and that was a good portion of his problem here.
Even on this touchdown, he's completely flat-footed and it's all arm:
That one obviously worked out, but as we saw here, he has so many where it doesn't. Sort of surprised he hasn't improved in that regard given that coaching staff.
Granted, the big reason for failure here as others have mentioned was the lack of protection and lack of skill players, but I would say that being completely alienated by your head coach was the ultimate problem, and I don't feel like Belichick handled that part of things well. Hard to function at a high level in this league, especially as a young player, when the person who is supposed to support you is essentially indifferent.
But, aside from that, unless Mac goes the route that Brady did and locks in on his fundamentals, footwork, etc, outside of preseason, I feel like those things will ultimately come back to get him if he ends up starting at some point again.