Publishers are very important. Fans, it depends on the expected circulation of the game. To a game with a small circulation fans are more important than to a game with a big name and mass market potential. The mass market dosnt sweat the details at all and as was joked about by some LA game creators , they dont finish games either.
You can disapoint the fans and get away with it,it dosnt really matter who buys your game as long as someone does.On the other hand screw your publisher and your sunk, especially these days where there are so few publishers.
There are many examples of games with very large fan bases which still made absolutely no difference at the end of the day.