From what I've gathered from your responses as well as a bit of researching, it seems like the goal of gender abolitionists it to eliminate gender roles via the elimination of gendered categories.

What I'm failing to understand is why eliminating categories is the solution. Moving towards a non-binary view of gender, where women and men exist as well as people in between, a mix, or outside of the binary model entirely is relatively attainable (we're already well on our way of having these facts re-discovered). As society progresses we'll continue to move towards eliminating gender roles, thanks to feminism and other human rights movements. The growing acknowledgement of intersex people will continue to show the not so black and white nature of birth sex, and with it shows that forced conformity to natal sex is illogical.

Considering these, I don't see the point in a move towards abandoning the categories. All these goals are attainable without doing so. In fact, every society (binary or not), has had a distinction at least between women and men. These ideas didn't spread because of colonialism, they're people categorizing themselves as people do. We find patterns and recognize them. An obvious pattern is certain humans with certain sexual organs giving birth. There's a necessity for a distinction, which is why it's historically been recognized nearly everywhere, including the people who fall outside the binary such Two Spirit, Hina, Hijras, etc.