My visualisation of sex and gender is of a woman's body with a load of junk accreting onto her, covering her, hiding her, limiting her movements and weighing her down. The body is herself, simply a human of the sex she is, and the accretions are the gender expectations society layers on top of her body because she is female and these are the things society believes and expects of female people.
So the idea that because most of the (modern) expressions of sexism sit in the Gender zone rather than the directly biological, biology is no longer a factor in sexism or even in the definition of a woman, and that we can look only at that accretion and not acknowledge that it is something women experience because of their sex and how others react to it, is wild to me.
The idea that a woman, who was born into that accretion and has been limited by it her whole life, and a transwoman, who was born outside it and desperately wants to be allowed it, are somehow the same thing rather than direct opposites, is wild to me.
Ironically, as opposites we could work so well together, us throwing the accretions off and trans women picking them up an enjoying them. Us pushing, them pulling, facing different ways but working for the same thing.
It is forcing the idea that we are the same that fractures Feminism, because it tries to force two opposite visions of womanhood into one shape.