I've been having this debate with Cowboys fans (I've got a bunch of friends that love them, for whatever reason) for a long time now, and it's just not true. In his rookie year, Dak had a 104.9 QB rating, and went 13-3 as a starter. In his second season, Zeke was suspended for 6 games, and he was trying to throw to Dez and Witten, who were both in their "final" years, and shells of their former selves. He had a tough year, but still led the team to a 9-7 record.
Last season, he had literally nobody to throw to in the beginning of the season when Dez and Witten retired,, and then they went and got Amari Cooper, and in the last 9 games with Cooper, he had 14t'ds (plus another 4 on the ground), 4ints, and a 103.0 QB rating, and led the team to a 7-2 record and then their first playoff win in forever.
Now., he's got Cooper, Zeke and Witten are healthy, and Gallup is turning into a player, and he looks just like he did in 2016.
He's not Tom Brady, so you can't expect him (or anyone) to light it up with literally no weapons around him. Give him a couple skill position guys, and IMO, he's going to spend most of this year as a top 5-10 QB in the league. The Cowboys would be insane to not work out an extension with him and try to start over with a new QB.