I do want to point out, Belichick is 70 years old. So I don't think it's unfair to say that yeah, maybe Belichick has lost his fastball in recent years too, but again, the guy is 70 years old!
I think Brady is 60% responsible for the dynasty, Belichick 40%, but lets not act silly and act like Belichick also didn't contribute immensely to it in the past 20 years. Brady isn't responsible for organizing and running the defense either.
That said, the NFL is a QB league. Like don't get me wrong, Andy Reid is a great HOF-caliber coach, but be real, are the Chiefs elite now primarily because of Reid or Mahomes? You can do a similar exercise with a lot of great coach-QB duos, the reality is the QB will get the benefit the most, but I don't think that's unreasonable. As Belichick himself has said numerous times after Super Bowls, it's "all about the players, they execute and put in the work"
Another quote is, "the coach's job is to not lose you games", and look at some of the dysfunctional teams around the league. It's mainly due to bad coaching. Unfortunately that also applies to NE in 2022, since they had bad offensive coaching (Patricia-Judge)