As a feminist my default reaction is to be sceptical whenever society determines it's necessary to treat men and women differently because it is so often based on sexist beliefs.
But I also recognise there are valid reasons for separation in some cases:
Firstly, where our bodies differ in such ways that we can't have equal provision without separate provision - sports, medicine, differences in physical tool design and safety equipment. These will never go away.
Secondly, where the intersection of our reproductive roles and the structure of our society put women at a disadvantage economically - maternity leave and employment rights, support for breastfeeding activities, legal obligation of males to finance the children they father regardless of the relationship with the mother. These will never go away as long as our society is structured around private incomes.
Thirdly, where the history of sexism in society has produced systemic structural disadvantages, internalised sexism and unconscious bias against women that has no root cause in a physical (sex) difference but nevertheless causes significant disadvantage, limitation or danger to women because of their sex. In this case we have agreed laws and other pro-women initiatives to counteract the reproduction of historic oppression. This I deeply hope will go away in future, but since these laws and protections can only be dismantled when the need for them has disappeared, here and now they are necessary. I personally include single sex toilets, accommodation, prisons and so on in this group because I believe that the male expectation of female care and time, male on female violence, male on female sexual violence and male fetishisation of female privacy is socially constructed not innate to male biology, but I accept I may be crediting them with too much here. Either way, as long as the danger is real, the protections are needed.
So all the reasons I can see where we justifiably separate men and women are either based in the actual physical differences, or inequalities that exist today because of past injustices based on those physical differences.
I also understand that under trans ideology, this view is hopelessly, irredeemably transphobic. To accept TWAW and TMAM one has to accept that there are no meaningful material differences between male and female bodied people that justify separation by sex rather than gender.
I don't believe that, but for the sake of argument let's say that is true.
I understand that while these sex-based separations may be wrong, since for historic reasons they currently exist, trans people want to be accepted on the Woman or Man side that aligns to their gender identity. However that's entirely a reaction and a reproduction of the pre-existing historic division rather than any practical difference between Man-the-gender and Woman-the-gender that produces an ongoing need for separate provision.
So while I know that feelings are not always logical, logically, TRAs should be fighting to dismantle these historic divisions that were based on sex, not keep them exactly as is but stick "for sex, replace with gender" on top.
And yet, they are not. So in fighting for TW in women's sports, women's toilets and women's prisons, there is an implicit statement in trans ideology that even without sex differences there is sometimes a need to separate men and women.
So what are these gender differences between men and women that mean we need women's prisons, sports, toilets, accommodation, STEM initiatives, political roles and so on?
Why under trans ideology do we still need to separate men and women in all the same practical ways that we were separating by sex, just now by gender and not sex?