None of those who dislike the first two are going to even bother looking at the store page for the third, and therefore won't buy or downvote it like they did with the first and/or second.

I guess you could say it's kind of a flaw in a one-bit rating system, like up/downvoting is. No way to let nuances be reflected in the score. If you just barely recommended it, or only recommend it for fans of the genre, it still counts as a 100% yes.