I think if there is a wishlist item that more people don’t want than want, then the comments on it will be obviously negative and that will be considered, not only the numbers on the vote count. Alternatively you could try to create an opposite wish and start voting there, which would basically be the vote “no”.
A good way they should approach is to make every wish they implement, where possible, optional. I know that’s not possible for every wish, but they could strive for trying to make any experience as customizable as possible.