Then you havent been paying attention to the whole story. Go back to his true freshman year, and he made TONS of the "OMG I need that guy" type of passes. But he also had a strong offensive line, and elite WRs, many of which (OL and WR) are in the NFL right now.
But last year, when those WRs graduated and much of the OL was replaced by true freshman due to the sanctions, he was sacked FOURTY FOUR times, and knocked down probably another 100 times. As a result, he struggled BIG TIME. He is still raw, but he has the tools to be a top flight NFL QB. I think you will see him step up this year.
Here is his freshman year highlight reel: https://search.yahoo.com/yhs/search?p=hackenberg+highlight+&ei=UTF-8&hspart=mozilla&hsimp=yhs-001. AS a true freshman he had poise, composure, made smart decisions, was a strong leader, and progressed through his reads in a NFL offense run by Bill O'Brien. Many college QBs look good because the players are open and they get them the ball. Hackenberg as a freshman was able to anticipate the play, and lead the receiver. Last year, under James Franklin, he regressed, but I attribute that as much to Franklin and the offensive scheme as I do to Hackenberg.
Assuming he declares, I GUARANTEE you that he will go in the first round. There is NO WAY Bill O"Brien and the Texans will be on the clock and not select him. ZERO. Someone is going to get a good QB. I hope its us. Actually I hope EJ plays so well we dont need Hackenberg...but it would be a good consolation prize if this season goes as I am afraid its going to.