The big issue in firing Joe, is that the person who would most likely do that is Brad. I don't think Brad is going to fire Joe. Now maybe ownership fires Joe, but that would imply that they want to actually win a title, instead of getting as many home playoff games without actually spending the extra money.
If it was an x's and o's thing only based on ability, wouldn't Joe already be gone? Seriously? We are one of 3-4 teams who are legit contenders. Are we going to waste another season with an inexperienced coach who can't get the best out of the team? If it was on merit only, or course we would fire him. But that probably doesn't have anything to do with it.
Only if Tatum and Brown and the rest of them basically revolted, and said fire Joe or we are all asking for trades would ownership fire him. They just don't have it in themselves to make that tough of a call, even if it might make next season a title season.