Feminism as a response to systemic injustice.
Instead of viewing feminism as an issue of progress, MacKinnon describes her feminism from the point of view of equality. In her view, feminism is the response to the systemic mistreatment of women and the historical inequality, some of which extends into her present day (and she would argue into the real present day as well).
Pornography as an attack on women.
One of the dominant features of MacKinnon's feminism is her opposition to pornography. Other feminists since have filled in the "sex positivity" aspect of these issues, which MacKinnon doesn't treat thoroughly. Instead she discusses the dark side of the market for pornography—the depiction of women as objects, the frustrating silence in response to years and years of sexual misconduct in the industry and the mistreatment of women in the industry.
Reforming the legal code from its male supremacy.
This is the thrust of MacKinnon's opinion as a legal authority. In her eyes, the development of the legal response to sexual misconduct is a good example of the vestiges from the misogynistic background of the American legal system. In other words, since women used to be viewed as property, there is inherent bias against women as the legal system tries to catch up to today's standards for the treatment of women.