Another thing that's possible to be true is that greatness as a coach is not a straight line. It can have peaks, valleys, and sometimes, cliffs.
Let me reiterate... Belichick pushed this team to unprecedented, unparalleled successes when it had no right to continue. The second group of three is a unique masterpiece of team building and gameplanning. The fact we came close on three other Super Bowls is just astonishing.
He is a first ballot, and to me, no waiting list, Hall of Famer. Canton and Foxboro. He should have a statue somewhere on the sidelines. If they ever renamed the Lombardi, it should be after him. I don't think enough praise can be given to the job he did.
His longevity was astounding. Consider Madden was retired and done for good at age 42. Cowher, retired and done for good at age 49. Guys like McVay and Shanahan publicly talking about retiring before they even turn 40. Even when you look at guys with long careers with one team, they usually had Super Bowl cutoffs. Most notably, you have Don Shula, who won two Super Bowls with Miami in 25 years. But none from 1974-1995.
Based on this, you have to say that Belichick OVERALL was the greatest head coach in the history of the league.
Yet, despite admitting to ALL OF THIS GREATNESS, I will still probably be called a 'hater' when I point out that towards the last few years of coaching in New England, his decision-making faltered, and he lost the desire to push himself when it came time to actually deal with any human. And unfortunately, being a HEAD COACH is more than just Xs and Os. You have to keep innovating, and challenging yourself with coaches and players outside your comfort zone.
And just like Don Shula in his last few years with the Dolphins, his coaching staff and players were all guys he liked or was related to. This sort of thing happens to the great ones, just like it happens to the rest of us.
Maybe that's why people defend even his obviously questionable decisions in later years. Admitting that heroes grow old is not one of those things we're comfortable doing.