If Brady had retired and the Pats had the exact same season, the conversation would be different. Anyone who has been a Pats fan since before 2000 (since the 70s for me) knows what ts like to be just like all the other teams or rather worst than most. But the reaction is really because many here wanted the Pats to go all in to get every last bit of QB play out of Brady before he retired. It was the opportunity to see this otherworldly run continue if even for just a few more years. This was especially true because there was no Aaron Rogers to Steve young in waiting on the roster when the pats decided to move on from Brady. Also some of the frustration at BB is that he seems to have bought into his "do your job" mentality in the sense that someone like Brady was not special and that Brady could be replaced as easily as any other aging player. That the Patriots were better that the 31 other teams because they were smarter than all the others in terms of roster building and because they werer simply the smartest team of all it was oK to never deviate from their cost structure and to not recognizing that maybe, just maybe the QB at the heart of all of their success might, just might, have had quite a lot to do with all of that success.
But this is all under the assumption that Brady wanted to stay. I don't think he did and I'm not alone in thinking this way.
Do people really believe BB just let Brady walk? For what reason would he do that? Before the 2019 season, Belichick signed him to a weird 3 year deal that was essentially a year to year contract. In that contract, Brady demanded he not be franchised.
Why would Brady make that demand if he didn't intend on leaving?
Whether it's because of Guerrero, sitting Malcolm Butler and possibly losing as a result, being tired of living in BB's shadow, or all of the above. The damage was done and Brady was checked out.
It's just like the ridiculous argument Red Sox fans make about Mookie. The writing was on the wall. He was a Boras client who wanted to test free agency. That means he's leaving for the highest bidder.
Boston fans have this weird arrogance to them where they think all players just want to stay on our teams and it's the ownership that drives them out. In some cases, that is true. However, in many high profile cases, it's not.
Players are mercenaries who do what's best for them (as they should). In many cases, that's about finding a team desperate enough to grossly overpay them (Mookie), or look for some "respect", or look to get out of the shadow of their coach, or leave the ****ty New England weather for a sunny area.
Tl;Dr - Brady was gone. Belichick knew it when he demanded the no franchise tag. Despite the winning of the late 20teens, Brady was growing disgruntled and that's that.
