A big difference between 2016 and now is he doesn’t have to look over his shoulder. He had to compete to win the job, and he did. That is on the FO to not have someone behind him to push him and make him continue to compete.
If there were a legitimate option behind him - we may see better play from Dak. Regardless, even if he were better, he’s never going to be great. He could be good enough to win games however and potentially big games (ala Dilfer, etc).
It would take guts, which Garrett is short on, but split some 1st team reps with Rush. Or sign Landry (or best available veteran, or try to make a trade), to show we have to improve there. Trying to will and want Dak to get better without trying to influence it isn’t going to change anything. The dude is too comfortable, he says all the right things, knows he needs to get better. He may be the kind of person that needs to have his job challenged to improve.