Saints planned to interview Mike McCarthy; McCarthy didn’t garner enough interest from Saints and will take a year off

I don't get this argument that since McCarthy has won a Super Bowl with GB he can't win one with the Saints...
No it hasn't been done yet.. but that doesn't mean it can't be done.

Andy Reid, Dick Vermeil, & Bill Parcells have been to the Super Bowl with multiple teams...

Sooner or later it will happen...

Now we're getting somewhere. I've already discussed Reid, but let's discuss the 2 coaches you mentioned. Vermeil took over the Rams when he turned 61. Yes, he won a Super Bowl. Came back to the game to win the Super Bowl. He went on to coach his third team, the Chiefs at about 65. Still pretty decent, just got old and eventually retired despite having a winning record.

Parcells started coaching at 41 years old and eventually won 2 Super Bowls with the Giants. I think he was on his 4th team by the time he got to the Cowboys. He was around 62. He had a winning record there before he retired.

Rebuilding a team in your 60s just hasn't proven to be worthwhile for these coaches to see it through if they've won it all before already. Reid still had the Super Bowl drive when he got to Kansas City. After a certain point, the will to do it dissolves even when they're coming off of good seasons.