You really think that is the issue? Not that he's never been a downfield passer and he's a 'Charlie Checkdown QB.. and that type of QB tends to look really bad when playing from behind.
Good accuracy, bad yards per attempt, bad at getting the ball in the endzone. That's his entire career, that's who we saw.
I've looked long and hard at his career and while I agree that he isn't aggressive by nature, under the right circumstances he will push the ball down the field. Using the Minnesota example and to play devil's advocate for Bradford, that team actually had a really shaky line and little to no running game. It was a good team with a really good defense but their o-line had it's problems and Dalvin Cook was injured for most of the year. Diggs was coming into his own and Theilen became a breakout star.
But they didn't have a running game and a lot of those short passes were by design not by checkdown. So, once everything came together and Bradford and his personnel had a season and offseason to work together they came out pretty hot in 2017. Bradford's TD%(7.6) and ypa(10.2) were both very good. We can't extrapolate but it does warrant wondering whether he would have kept those types of numbers up had he stayed healthy? He was in a system that he was not only familiar with but also comfortable with and it was clicking.
He hasn't had that luxury in his career so there is the possibility that that sort of continuity would help with his numbers. Comfort and familiarity with the Cardinals is something that I've been concerned about with Bradford. He rarely starts fast but I'd hoped with Fitz and DJ that he could lean on them at least in the beginning. Apparently not.
My point is, Bradford can be aggressive once he gets comfortable but he's rarely comfortable. I was pretty disappointed with this first game. I suppose it's understandable since it's a new offense, new QB, new receivers, hurt TE, etc.