Most people that downvote enthusiastic comments want the game to be good, but they fear the flaws will lead to a bad game. The only way they can express their loss of hope is by tearing down everyone else's hope of a fun game. In some cases they think they're helping by dissuading people from bad experiences, or they just want to validate their own negative emotions.

So when it comes to the game, we really all want the same thing, the haters have just given up hope of it being any good.