It's amazing to me how the so-called draft experts and pro scouts can't evaluate college QBs worth a sheet. So much of how well a QB does depends on what team drafts him, what system he has to learn (and try to master) and what coaches believe in them.
For example, would Carson Wentz his rookie year (if he had been drafted by the Browns) have done significantly better than Deshone Kizer this year? Probably not.
Look at Kirk Cousins. Why was he a 4th rounder? He's not very mobile, he shorter than desired and he doesn't have a cannon arm. But, he's very accurate and he competes at a very high level---which the days will get you $28M a year.