The highest rating on Rotten Tomatoes is not given to the best movies, it is given to the movies with the least amount of flaws. Controversy won't get you over 90% which makes sense, the rating should be read as 90% of people enjoy this. One reviewer didn't rate it at 90%, 90% of reviewers rated it positively. I am coming to terms with this. I'm starting to think the best films are rated between 70% and 85%. Not too many obvious flaws, but an enough character to be divisive.
70 to 85