I agree that many NFL teams don't look at it that way, but then again many of those teams are stuck in a loop of poor performance from certain positions.
I can't think of a QB who after not looking like a franchise guy in 3 years turned the corner for that same franchise. I would argue with myself that Mitch looked like there something there in 2018, but much like Marcus Mariota looked after year 2 when things regressed it's time to cut bait.
As an overarching theme I wish NFL teams were more patient with their coaches and less patient on their high draft picks. Two things are critical in my opinion: culture and talent. Culture is largely provided by the coach, so you want some consistency there. Talent is mainly on the players and when it's not there teams should move on.
Pegger... the reason the patriots are great, is because they dont switch QBs they switch schemes.
Some games they are a power run team. Some games they are running 2 TE sets. Some games they throw from the shotgun 40 times. Some games they lean on screens and PA passing.
The thing about Nagy is.... everyone knows whats coming next week. The scheme will be the same and no adjustments will be made. The offense will score a head scratching 17 points.
Its not the QBs. It's not that the coaches are bad. Every generation you only have a few genuis minds as HCs, and a few superstar QBs, having 1 of those gets you playoff appearances. See Andy Reid, John Harbaugh, Mike Tomlin and Belichik. Elite QBs, Brady, Rogers, Rivers, Ryan, Roethlisberger and Mahommes.
If you put them together you get superbowls and deep playoff runs.
These coaches all win regardless. Because they scheme to fit the team. These QBs win regardless because their talent is above the rest.
Chicago has a young QB with possibly the most stubborn playcaller in the NFL. No QB will win with a stubborn playcaller.