How bad was this season

The sad truth is this. Look at the Colts after Manning. The Broncos after Manning. The Pats after Brady. The Packers after Rodgers. The Saints are not unique. This is likely the new norm. And the most likely scenario is that the next HC will also be fired after 2 or 3 years. Because that's the norm for the NFL with only a few exceptions. And the Saints are no longer one of them.