I think there are a couple factors at play: firstly, this movie is actually pretty silly and weird; although I disagree with the movie's politics, it's a good film, and I like it. However, it felt a lot more like a cult hit than a mainstream blockbuster success. I can tell why some people wouldn't like the film due to it's weirdness or how much of the plot doesn't make sense.
But also it's a highly political film, so there's a lot of subtext, jokes, and moral messaging that probably won't connect unless you're fluent in American politics and the three waves of feminism that have swept the nation.