Let's focus on some critical thinking. Many people assume here that because the women "partake" in the culture, it must be okay. Or many assume "the men in Japanese culture are better because the women don't naturally excel in the same fields as much". So they assume the women in that culture do "worse" because they are innately worse rather than questioning, "what if the reason why they do worse is because the culture encourages them to not excel in those areas to begin with? Are there any studies that show there is a significant innate biological inferiority of women compared to men?" As it turns out, there are no innate differences in intelligence betweem men and women, and any areas where one on average does better than the other are not significant differences, and usually there is an area where they do worse to balance it out. So the studies done don't show any significant correlation between sexes and intelligence or areas of intelligence. Yet the higher intelligence requiring fields in Japan are occupied overwhelmingly by men. This is not due to a biological factor, and therefore must be due to a human-made system or concept. Culture is the best fit for this. Sure there could be other factors, but they are not consistent when compared to other countries.
Also, women's studies courses use statistics, logic, and critical thinking. They use other things like opinions and ethics, but it's a field of philosophy, so it's not unwarranted. As is the field of cultural studies. There's no right or wrong answer. In the end it's all just opinionated bullshit.