The march was about a lot more than women's rights. If you are lucky enough to not feel like a second class citizen, or if you've never felt in danger or worried because of your gender, you're very privileged. Thousands of women in this country are still in situations where they don't have the right to go out and get a job, where they can't get access to the support they need, be it emotional, mental, or healthcare-related. There is the wage gap, the rape culture issues, and plenty of other women's issues that I, as a white man, can't even articulate because I've never and will never know what it's like to be a woman in this country.
However, it was also about LGBTQ+ rights, standing up against Islamaphobia, and there was a presence of many other groups, including anti-abortion, pro-choice, Black Lives Matter, immigration, and other rights groups.
The aim, basically, is to show solidarity with women (and men) the world over. That's why there were sister marches in countries all over the world (even in places like Cambodia, where they're technically not even allowed to protest). It was as much pro-women and pro-equality as it was anti-Trump/etc.