Andy Reid had never won a Super bowl before the Chiefs.
Belichick had never won a Super bowl before the Patriots.
That's not the same.
And you're ignoring that one of the people from your example, only got one sniff at head coach last year. Nothing I said was inaccurate. Show me a former Super Bowl winning coach who has rebuilt another team into a Super Bowl winner. I want the Saints to contend for Super Bowls, not be good enough to be competitive.
McCarthy wouldn't be horrible, but I'd prefer the odds if we give a new coach a try. Could it fail? Yes, but at least the Saints will have tried something that has a track record of success versus something that doesn't. And again, hoping that a former Super Bowl winning head coach over the age of 60 gets his third different team to the big game doesn't have a history of success. Young, motivated new coaches does though.