If we have Mayfield, Darnold, and Fields all performing decent/good with new teams I'd say that's a strong indicator that QBs can be ruined by bad organizations. Which brings up the question: how many of the Bears' QBs were misses in scouting and how many would have been at least serviceable if not for the ineptitude of the coaching? With a guy like Caleb, it's hard enough to become a good NFL QB without having to swim upstream navigating terrible coaching and gameplanning at the same time.