What I tend to find is that most of the time, complaints are a sign of a problem, but not specific to what the problem is. If someone dislikes a game, they generally won't understand why, so they'll reach for the obvious and public culprits. It's not what I think this type of game should be. It's dumbed down. Etc. The plot sucks. When the impacting factors are sometimes more subtle and less recognized.
That is to say, when someone likes a game, they forgive the faults. When they dislike a game, they'll complain about any element of it, regardless of whether or not that's why they actually dislike it.
This is the role critics are supposed to fill, by my understanding. People who actually know enough to point out these elements and understand how they contribute to the overall enjoyment of a particular game.