Can't see the point of the marches
I don't know about the rest of the world but in the US it may very well have been the first protest march a lot of these women have ever been on. By registering they are now in touch with grassroots organizations that can help co-ordinate and organize their voices in letter writing and emailing campaigns, in helping publicize the abysmal performance of DeVos and what she did to education in Detroit, to campaign to get the gerrymandered district boundaries changed in time for the mid-term elections etc.
You make a good point that advances in women's rights typically mean the advancement of white women's rights while minorities and those in patriarchal societies are left behind, but disenfranchising white women and sending them back to the 1950's isn't going to help.