Even haters can admit that Belichick is a great defensive coach, but it's also true that he hasn't been winning as many games post-Brady. So, picture this:
But, one of his non-Brady rosters won 11 games with Matt Cassel starting at QB. In 2008.
And even in these post-Brady years, they are still around a .500 team. Not good, but certainly not bad either. They also managed a 10-7 season and postseason birth in 2021 with a rookie Mac Jones playing QB. If that doesn't signal good coaching and "team" contributions, I don't know what does.
They lack explosive play makers on offense and aren't quite the rushing team they've been, yet they remain a formidable team.
It seems most are enamored with Justin Herbert and his talent even though he's a .500 QB at 26-26 as a starter -- "what if" the Cheatriots had him as their starting QB with the same roster they've got now? They'd almost certainly be better than the .500 level team they've been.
Again, it takes a "team" to win, and the Cheatriots field good all-around teams much of the time. If they have a good QB, they seem to succeed very well. And even when the QB play is subpar (Brady wasn't good in 2018, Jones isn't all that good now) they still manage to be competitive and/or overachieve.