I don't know what to tell you. McCarthy got run out of GB for his failures. His offenses became stagnant. He couldn't get another job for a year. His hiring in Dallas was met with skepticism, when he named himself OC in Feb, again a lot of people were skeptical given how he bombed out in GB. In the meantime, a creative, first time HC turned Rodgers around and the team was quite successful and Rodgers had two great seasons.
The evidence is there that McCarthy is what we see - average, decent, mediocre, something in that range.
It's perplexing that people think he's actually quite good but then again, we had people defending Garrett right up until he got fired.