Maybe I misunderstood your post with regard to Gay Days.
I'm not weighing in on how scientific the methodology is. It doesn't really matter to me. TripAdvisor is pretty reputable, IMO if in no one else's, but I don't think I'm alone. The list is something to consider. That's all. It's not as though I take whatever is at the top of the list, and decide - we're going there. It's just something to consider. In fact, when I'm going to a new city, I will look at the list of top attractions there. I may discard the 6 most popular attractions as things my family would just not be interested in. I like lists like this, but they're just one tool to consider.
I still think any issues with methodology would affect things across the board, and not disproportionately affect Disney. If people are rating too high, they're doing it across the board. If people are only complaining and not praising, they're doing it across the board. If some people have looney-tunes complaints, the looneys don't just weigh in on Disney. If only the kind of people who leave reviews are the ones weighing in, then that's true for all theme park reviews, not just Disney.