Most college football quarterbacks are not elite. Attempting to pinpoint why is a maddening exercise that takes you down many a rabbit hole.
Ultimately, the weaknesses that stop guys from being top-notch talents are plentiful. They come on the field and off the field. There are flaws in their skill set and players that don't fit into systems. All of these things keep players, from 5-stars to none whatsoever, to growing into top-notch signal-callers.
As far as player-controlled weaknesses, physical flaws, limitations and mental hurdles keep guys from reaching the pinnacle of success. Physically, the inability to make all of the required throws, escape trouble in the pocket or be a running threat has kept many a player off the field and buried on a depth chart.
Coaches have found a way to be successful with limited players, thanks to systems catering to what they can do, but the bar for being an elite quarterback is still one that most guys playing never clear.
Mentally, the transition from one- or no-read high school football to the complexities of a collegiate system is tough. The game is faster, the pressure is higher and college coaches expect players to do more than just go out there and wing it on their natural talent.
That means knowing the playbook. Understanding the different concepts that your coach wants to take into games and how each concept fits into the larger scheme of the game plan.
For some kids, it is just too much. They might get on the field, but a cut playbook limits not only what a player can accomplish, but what a team can expect out of the offense as a whole.
Essentially, a quarterback who does not have a firm grasp of the playbook is akin to a boxer trying to do their best with one hand tied behind their back. You might beat some folks like that, but you'll never get to the top level.
Being incapable physically, or mentally, is on the player. Hard work can eliminate some of those aspects, while others are merely plain points of fact. You can't make yourself taller or somehow grow a cannon for an arm.
However, for a player, the more frustrating weaknesses are the ones that are not your doing. Coaches changing jobs, leaving you in a lurch with a new position coach who wants "their guys" to play. Entire coaching staffs getting promoted, or fired, leaving you there, with a new system. Quarterback coach going with youth instead of you on the depth chart.
Those are the ones that hurt. The player did not do anything wrong. Basically, he was just the odd man out as the rug was pulled out from under his feet. Coaches do not usually apologize for it. Players have to make the decision of riding it out, making the most of it or picking up the pieces and moving to a new location.
In the grand scheme of things, quarterbacks are not special. The things that keep them off the field or from becoming big-time players are the same for the signal-callers as they are for every other position.
Those issues are merely magnified for the quarterback position because you can only play one, and most quarterbacks cannot play another position or help out on special teams.
Physically, plenty of players do not make the cut because of their limitations. For others, the mental aspect is what holds them back. Yet, even if all of those things align and a quarterback sets himself up to succeed, it can all be submarined by factors that are beyond your control.