Multiple things can be true:
Tom Brady is the greatest QB of all time.
Numerous coordinators were good to great and still made shitty head coaches.
Belichick was a Hall of fame caliber defensive coach before Brady was playing college ball, let alone in the NFL.
Neither Bill or Brady would have six rings without one another, as together they were the perfect storm.
God, I was so excited for the Patriots to finally suck but the inane hot take merchants have me wanting the Pats to make a deep playoff run just to shut them up I fucking hate this.
Funnily enough, your last line about how no one else could win with this kind of QB play made me wonder, and:
In the Browns six wins, they have average QB play of 19/32.8, 208.33 yards, for 1 td and 1 int,, for a rating of 73.8.
So. Maybe it's just an AFC North thing.