I haven't been a supporter but I'll defend him for a second. He is who he always has been. A product of the players and scheme around him. When everything is clicking, he is more than capable of executing the role and looking pretty good. When things are bad around him, he looks bad. That is the case now.
On one hand, I'm pretty confident that if you improve the line and the run game and WR2, Dak will go back to being around the 10th best QB in the NFL.
OTOH, you can't make guys like that the highest paid player in NFL history. You just can't. Guys like this are available in the offseason regularly. Russell Wilson is playing on a vet min contract. Winston looked pretty good on Sunday. Mayfield is playing like a top 10 QB. All of those guys were formerly in a situation like Dak is now, took the blame and then moved to a better team and look better.
Unless you have a truly great QB (and that includes the ability to run), you can't give out a mega deal like this.