Agreed. This is one of the most critical fanbases around. It's part of the "whine and cheese" crown thing too. If they aren't winning, Cowboys fans get disgusted far more easily than other fanbases. They don't show up and get excited unless it's a Super Bowl contender.
Also one of the reasons why a couple of 8-8 seasons means we have "one of the worst coaches in football" instead of a merely average coach that the record indicates.
That being said, we are the Cowboys, and we should expect more, and if the coach can't do better than that, he should be replaced. Jerry Jones can easily do better with his resources and doesn't.