I don't see it as sad in the least. The only thing I am sad about is the Patriots losing the last 1.5 seasons. It was fun at times to talk about BB's legacy. And I liked the idea of our team having the GOAT coach, but only if he truly deserves it. I'm never sad to see someone get the recognition they deserve, positive or negative.
If BB isn't the best coach of all time then I'm not sad about him being 'exposed' when his record, accomplishments and legacy were built upon by things he had little to nothing to do with. I'm only sad that it has to happen at our expense. If Bill really can't build a consistent winner without Brady, then he doesn't deserve to coach a consistent winner. And he doesn't deserve to have the reputation he does. That being said, it's too early to say that as of yet. His legacy has taken a hit, but it is still recoverable.