I never said he was.
I said sometimes what a team needs is a coordinator change. This can be true no matter how good the head coach is. If Sean Payton never replaces Gary Gibbs, it’s entirely possible 2009 plays out very differently. It’s very possible that a strong offense and a bad defense may sneak up on a league for a season but will stagnate more and more over time because other teams are trying to scheme against you too. Gibbs has never been hired to coordinate a defense since.
Sometimes all a team needs is a coordinator change.