I think the question of what Caldwell brings over an average coach is a great one. Obviously there are the things we can't really see as fans: do players like/trust him, does he motivate people, does he have a great eye in the film room. But, where does Caldwell rank in the things we can assess?
Does the team come prepared for every game? Do they appear to know the opponent's tendencies and adjust their tactics to squeeze out advantages? ... No, clearly not.
Does he manage the clock well, giving the team time when it needs and chewing up clock when the other team needs it? ... Jeez, Caldwell might literally be the worst time manager in the game right now.
Does he challenge well? That is, does he throw the flag when it's likely to go his way and does he hold the flag when it won't? Does he throw the flag when a play really matters, or just to get 3rd and 2 instead of 3rd and 1? ... Caldwell is actually pretty good with winning challenges, consistently winning half or better of his red flags.
Does he bring a positive identity to the team, consistently bringing out the best in a specific group or area of play? ... Given the wildly inconsistent play on both sides of the field, and the relatively invisible upgrades (not related to getting better players) to any groups, I can't think of what identity he might bring.
So basically, Caldwell is good at calling challenges, bad at managing time, and makes no discernible difference anywhere else. If we consider him at fault for the poor starts to games and his choice of coordinators (JBC), he only falls below average. I wouldn't be terribly upset if they kept him until they could opt out, but I really don't see anything about his tenure that screams "keep this guy." Caldwell seems like the poster boy for coaches who won't kill your team, but won't make them any better either.
