Let us assume they are correct and other coaches with track records similar to Garrett would have been fired by now. So what? That, by itself, does not invalidate Jerry's decision to stick with Garrett this long. Like I have said in the past, there is no absolute mathematical formula for determining success in building a football team or how long a coach should get before he is fired. Coaches get fired when a front office decides they have reached their potential for growth and they still aren't winning at a high enough level. That decision is usually rooted in criteria that are both subjective and highly qualitative.
I wouldn't shed tears if Garrett was fired, but he shouldn't be fired unless they can replace him with someone obviously better, like Sean Payton.