The MPA gave the movie an NC-17 rating "for some sexual content." NC-17 is a higher classification than an R rating and means no one under 17 years old can be admitted to see the movie, whereas for rated-R films, those under 17 can see the movie with a parent or guardian. Blonde is set to stream on Netflix soon.
Unrated is a movie that has not been rated by the ratings board of the MPAA, it does not mean it's "worse" than a rated R movie, only that it simply wasn't submitted to be rated.