A new coaching staff is what Dak needs. He is what he is- an upper middle-tier quarterback.
If you give him a running game, more than one receiver, solid protection, and good support from his defense, Dak will win you a lot of games.
The Cowboys have none of that this season and we see the results. Even as a Dak fan, I realize he is not (and never was) the type of quarterback that can single-handedly carry an entire roster. However, how many quarterbacks are?
If you want proof that it takes an entire team to win, look at Joe Burrow and look at his stats. Now look at the Bengals' record. He can't do it alone.