Do you think "designated toilets" occur in biology? That sex-segregated spaces, in and of themselves, are anything but a part of society's gender norms?
Now this one is a good question and it's worth unpicking.
They are indeed a part of society's gender norms, but not because society just capriciously decided sometimes we would separate people by their physical sex.
Leaving aside those that exist entirely due to physical differences (sports, contraception, maternity leave, different toilet types, clothing shapes and sizes), women-only spaces, rights, protections and opportunities reflect society's gender norms to the extent that they were put in place to mitigate the social gender norms that allowed male-bodied people to physically, spatially, socially, culturally and politically overpower female-bodied people.
They are a reaction not a cause.
And those male-benefitting gender norms were not themselves one thing but the combination of physical power, historic laws that explicitly disempowered female people, cultural norms that associated male voices with more knowledge, trust and authority than female, socialisation of males to compete and females to defer, imagery of females as passive prizes and plot devices and males as subjects and agents, and so on.
So absolutely, I would welcome a future where female-only provision is no longer needed because the old, sex-aligned social gender norms that they protect us from have genuinely gone away. That, after all, is what Gender Critical Feminism is working towards. And if that's what your vision of a gender-norm free future is the same we should be gladly holding hands and marching towards it together side by side.
But if your vision of a gender-norm free future is simply to ignore the historic and ongoing disempowerment of female people, dismantle all single sex protections in order to make them a multi-sex validation of self-defined of gender identity, and through that somehow all those pre-existing sex-based gender norms that disadvantage female people and made single-sex provision necessary in the first place will magically go away without you ever having to tackle the difficult and real underlying problem of how males (of any gender identity) feel entitled to treat females.... no thank you.