Let's take a step back then. It seems people are arguing against retreads, correct? If there is a different thesis, I'd like a specific statement people stand for rather than general bitching. I can understand a specific thesis.
If the argument is against retreads, I agree to a certain degree. Norv Turner as an OC had his last truly great coaching year carrying an average Miami offense in 2003, yet he is getting another chance.
At the same time, are you keeping track of all the young position coaches who get promoted to OC and aren't ready? It would be a long list, including Zampese in Cincy and Downing in Oakland. Sometimes they grow into the new role, sometimes no.
If you look at the success rate of college coaches getting a pro job, they usually spend a year as a position coach before getting playcalling or coordinator duties. That is because the speed and size of NFL defenses is such a huge leap from college to the pros. Members have explained the vast difference between the college game before - wider hash marks, larger rosters, grown men instead of college kids, etc.