Dak has already proven all his critics wrong. He's been doing it for years.
BWAAAAAAAAAAAAA!!!!! Dak had the starting job fall into his lap? Dak beat out the encumbant Romo ON THE FOOTBALL field in games. He did that his rookie year when the team won 11 games in a row with him as QB. Heck even Romo was caught on camera on the sidelines declaring that Dak had earned it after the comeback win against Philly.
https://www.nytimes.com/2016/11/16/sports/football/tony-romo-dallas-cowboys-dak-prescott.html
“Dak Prescott, and what he’s done, he’s earned the right to be our quarterback,” Romo said. “As hard as that is for me to say, he’s earned that right. He’s guided our team to an 8-1 record, and that’s hard to do.”