Yeah, most review sites have the 5 or nothing problem. I look at the distribution and then find some medium to low starred reviews to see why I might not like a book that otherwise seems a good match for me.
In aggregate the star rating is pretty good for literature and non-fiction. For mass fiction it's fairly useless.
But that's a problem with people doing the ratings, not Goodreads. I see this problem with IMDB, trakt, myanimelist, anilist, etc... Because for many people, it's either 1, 4 or 5.
In aggregate the star rating is pretty good for literature and non-fiction. For mass fiction it's fairly useless.