Bare with me on this long post.
It's an accumulation of things in my opinion. (These are just my opinions, disagree if you'd like)
1. (The obvious) His health. Anyone who's played and been injured know that coming back from injury can severely limit you. (Example) If you know your leg isn't right, then you try to use another part of your body to help you throw the ball.
2. Confidence in play calls - I think MM has told Dak not to audible out of plays as much, thus you see the WR screens on 3rd and 7 instead of lining up and firing it. (He may have to go to Jones for permission as Romo did) but that's selfish IMO.
3. Defensive Strategies - Back when he was tearing up the league, his number one target was always Schultz and now it's rare to throw to him. Just as in the Witten days, Witten was his bread and butter. If defenses are taking Schultz away and CAN take him away, we need a dynamic
TE that can cause fear in the middle of the field, either that, or Moore/MM needs to scheme around them. OR, Dak doesn't know how to
survive without the comfort of his TE, and he needs to learn to.
4. WR - If you play against NE the first thing they do is to identify your #1 threat and take him out of the game - once that happens, you take the #2 out of the game which is Schultz. From there you try to beat guys up at the line and ride them. Ceedee is showing his inexperience as a route runner. When you're not where you're supposed to be or looking over the wrong shoulder, dropping passes etc, the entire process
breaks down. Once Ceedee has the ball in his hands, he's deadly, but to me, he doesn't know how to effectively use his body to post up defenders draped on him, none of our receivers are good at that. The perfect example of a receiver who used his body well, Dez Bryant.
In another year or two, Ceedee will be the perfect receiver, but he's not yet.
5. Offensive line - The line had it's best game last night but you could tell Dak had a little PTSD from previous excursions/games. It was like he was seeing ghosts that weren't there. If you learn to move around in the pocket as Brady and Rogers do, you will have all of the confidence in the world. You don't always have to escape the pocket, just reposition yourself in a more clean area of the pocket and or completely abandon it by running. But I don't think Jones wants Dak running. At times you see Brady with 8 or 9 seconds to throw the ball, and at times he fires it off in under a second. He repositions himself in the pocket, has an idea of his hot read, and when he's in terrible trouble, he goes down before the crunching hit and that's why he's 44 and still playing at an elite level.
6. The run game - His favorite piece of arsenal has abandoned him. Get this run game going and see the old Dak.
Summary: Unfortunately Dak is not Rodgers with elite arm talent, or Brady with elite intelligence, or Kyler Murray with elite movability, but we can win a Super Bowl with him if we use him properly because he has a little of all of those qualities. QBs don't grow on trees and you could spend a lifetime finding one, ask Washington and a plethora of other teams . Garrett and Jerry Jones wasted Romo, but you have to learn to use what you have, and that starts with building a first class defense to help your QB. Our defense saved us yesterday, and our defense should be able to save us at anytime.