Bill Belichick is the greatest coach of all time.
What Brady's departure exposed was 2 things.
1) Franchise QB >>>>> Head Coach.
We've seen it before HoF Coach leaves and the team keeps winning because they have the QB(s). Walsh leaves the 49ers, they keep winning. Holmgren leaves the Packers, they keep winning. Bill Cowher leaves the Steelers they keep winning. If Andy Reed retires in a few years, the Chiefs will keep winning. If Pete had retired the Seahawks would keep winning, and as long as he has Russell Wilson he will still keep winning.
Pete Carroll his first 2 years with the Seahawks did an excellent job. Yet he only went 7-9 in back to back seasons. Then Wilson showed up, and double digit wins became routine.
2) Bill Belichick the GM is underwhelming at times.
Loves to penny pinch, will cut good players, cutting off his nose to spite his face, even if it really isn't necessary. He trades down so much, they seemingly trade themselves out of drafts. Cannot draft WRs to save his life. Doesn't value pass rushers as much as he should. Coaches up players and has them playing above their talent level. The flipside to that coin is, they aren't as talented as they're playing. His arrogance makes him believe he can coach just about anyone up. He is kinda right, but he could make things easier on himself if he got more talented players.