William Stephen Belichick started Drew McQueen Bledsoe over Thomas Edward Patrick Brady, Jr so the answer is no. No one knows anything. This isn’t Madden, there’s no database of ‘actual’ ratings. You can win with backups and Joe Flacco and Joe Namath and sometimes even with Tim Tebow or Urban Meyer.
They figure it out and second guess themselves constantly. Even now, reasonable coaches can argue about how good Russell Wilson really was in his prime, and how bad Zach Wilson actually is.
Even Brady, the acknowledged greatest QB of all time, was barely winning games early on but was on a great team with excellent coaching. BTW, Brady has good size and throw but his real super power seems to be that he out-homeworked everyone else, to get rid of the ball fast because he had a good coaching staff early and worked on reading the defenses and connecting with receivers. He trained constantly with receivers before there was a limit on it, until the timing was perfect, and he got receivers to buy into it, no doubt helped by an early Super Bowl and ‘bad cop’ Belichick. He also bribed the OL and later in his career was obsessive about his health. NONE OF THAT could be measured in college, it didn’t even exist.
Manning came in with ‘pedigree’ and knew how to run an offense by himself, at al all-star level. But Eli did too, and he was a goofy lucky turnover machine with excellent mentoring. Everyone ‘knew’ you couldn’t teach accuracy until Josh Allen happened. Everyone ‘knew’ that Doug Flutie was ‘too short’ 20 years ago but Bryce Young still got drafted last year. Nick Foles was a backup, Wentz was an excellent starter, Jimmy G was a good QB, and Mac Jones was considered an all-star.
Fans and owners love blaming coaches, but the most successful franchises keep people around.