For years it seemed that if the Cowboys lost their starting quarterback, their season was over.
Back in 2015 when Tony Romo missed just about the whole season, the Cowboys couldn't piece together a backup plan to win games, ultimately finishing 4-12. In 2016 Romo got hurt again, but luckily then-rookie quarterback Dak Prescott was there to save the season.
The only backup quarterbacks ranked above Dalton were Jameis Winston and Marcus Mariota, the top two picks of the 2015 NFL Draft. It's hard to argue against those two considering both were recently considered top prospects and future franchise quarterbacks. It didn't work out, obviously, but Dalton brings a different skillset to the table than those two.
Dalton himself as fallen off a bit in recent years, but as PFF mentioned, this supporting cast is nothing like he's seen before. If he was forced into games this season he would be surrounded with three potential number one receivers and one of the league's best running backs. That surrounding talent combined with his veteran presence would likely be enough to keep the Cowboys afloat for a few weeks.
As a backup option Andy Dalton is as good as the Cowboys have had in years, but he's certainly not challenging Dak Prescott for the starting job any time soon.
This offense is put in place to go crazy in 2020, and even their backup quarterback is considered at the top in the league at his role.