Do we "need" the fans at the stadium? Well, that depends on whether you think having fans at the game affects the outcome. I happen to think it does, perhaps you don't. But if you do, then these kinds of variables -- and the Dolphins' total lack of awareness of them -- should be important to you. It's a lot easier to fix the stadium than it is to fix the demographics of Miami, donchathink? The way the situation is now the stadium and it's location help keep people away, which makes the team worse, which means more people stay away... around and around the toilet bowl until you've got the situation as it is now.
A better stadium in a better location would incentivise people to show up even with the team mediocre as it is now, which could be the spark the team needs to get better and get more people coming to the game.