Honesty I think there's no objective way to rate a race. Its own name says: rating; it's totally open to a variety of opinions.
A race should be assessed depending on how easy it's for all players to pass successfully. I have hundred of view points about the same race related to the vehicle it's used, the weather they set, the city we're in and how long it takes to finish. That's mainly the reason I use /Like and /Dislike to remember a race which I enjoyed or not. After I type, it appears on the menu assigning a (L) or (D), so it helps me to avoid voting for what I don't want to.
In an unadorned way, it's pretty hard to rate sincerely a race, so you all shouldn't care so much about what people say unreasonably but what they can explain reasonably and your experience tells you.