The thing with Brady is he brings a lot more to a team than just what's on the field on game day. Look at the Bucs.
So why couldn't he have a winning season anywhere he goes?
The Bucs' Winston ut up 510 passing years the year before Brady went there. OJ Howard, Cam Brate, Mike Evans, Chris Godwin - all there (Evans and Godwin put up almost 2500 yards between them with Winston), as well as top 10 picks - Vea, White, Wirfs - all over the place. power rankings had them around 5th before the season started for a reason.
Of course, Brady made a huge difference. Of course. But that team was only a couple of pieces short, and they got the best piece of all. Without taking anything away from Brady, the GOAT, I think that if, say, a Murray or Allen or Mahomes or Wilson went there (and Gronk, AB, Fournette, etc. join in), they probably still win the SB.
And a great QB (only that position in today's NFL) probably means more than a great head coach, but it's closer than you seem to admit.
Would Brady have been given the chance to become the goat without the Pats and BB? Maybe, but I wouldn't put money on that. He was a big part of the 01, 03, and 04 wins, but so was Ty Law, so were McGinniss, Seymore and many other great players, and so was, particularly in '01, the best coaching.
Without Brady, but with another competent QB, I'd guess that BB wins 2-3 SBs. Without BB, IF he was given the chance, I'd give Brady about the same. Happy to see them together for so long, sad about how it ended. Brady should be breaking all the records in a Patriots' uniform.