The argument you're presenting (more eloquently than most here) boils down to this: the Patriots way has worked for 17 years, so it will continue to work.
But this off-season, Belichick has not adhered to the Patriot way, or at least not to Patriot custom. He gave a non-Patriot free agent a long term, $65M contract. I don't think he's ever given a non-Patriot a contract anywhere near that large. Neither Moss nor Revis got anywhere close to that number. So the Gilmore contract represents a sharp change in philosophy by Bill. And if Bill can change his philosophy, then you can't use the success of the old philosophy to predict the success of the new.
If it works out - if Gilmore really is worth that - maybe it makes sense (even then, jealousy and agent demands by other players on the team could ruin things). But as I said above, if that contract doesn't work out, then how does Belichick expect to maintain the chemistry and cohesiveness exhibited by the 2016 group? How do you persuade players to sacrifice salary when the savings are squandered? Or play for the team when playing for stats is rewarded? It's too early to say if the Gilmore acquisition will pan out. But it's not too early to say that (1) it's a sharp change in Patriots custom; and (2) if it fails, then the ripple effect on chemistry and salary demands could bring down the entire dynasty. Many teams in many sports have been shackled for years by such contracts.
As for your other examples, these typically had to do with failing to meet salary demands or behavior issues. The loss of Blount, Long, and Bennett doesn't seem to have had to do with that so much.
So the argument: "oh we've seen Bill jettison vets before" doesn't apply. Because he's never done anything like the Gilmore deal, and particularly not in conjunction with letting so many smart, valued vets leave.