Dak clearly did have confidence issues after week 7 last year, hopefully an off-season studying tape and recovering from his injuries will help.
I think his problem had more to do with the reinjury. If he lost confidence, it was in his body and it affected how he threw the ball. Again, some of that was pointed out by one broadcaster, how he was lifting his leg off the ground during his release. There were throws he missed the second half of the season that he just wasn't missing the first half. That's all it takes. Throw behind a crossing route on a second down and it's third-and-long and maybe the defense gets a sack or enough pressure to disrupt the next play.
For what it's worth, Prescott has had trouble throwing behind receivers in past seasons, but he seemed to have cleaned it up. Then the second injury and he reverted and was even worse with it at times. I think this offseason needs to be spent rebuilding confidence in his mechanics, making sure that he feels if he plants the back leg, it's not going to buckle, etc.
Yes, there are some things schemewise we need to do as well, but if Prescott had hit some of the throws that he missed, that would fix some of the scheme problems. Getting Elliott healthy and improving the offensive line might fix some of the others.