Men cannot be women, nor women men because they possess mutually exclusive essential accidents, viz. maleness and femaleness.

Since sexual dimorphism is part of essence of human being, one’s sex is an essential accident, not a mere accident that could be changed.

An essential accident is a something that flows from the essence, viz. “human beings are either male or female”, and is an accident qua which you are — neither is essential to being a human being, but being one or the other is.

Intersex persons are not non-males and non-females but either males-with-a-developmental-disorder or females-with-a-developmental-disorder.

The necessary and sufficient conditions of being a woman are mature human with a Bauplan teleologically directed toward conceiving and bearing young.

No MtF trans person shares this Bauplan.

This does not mean that in some cases of extreme gender dysphoria an attempt to pass/live as the other sex is not the best option in the circumstances. It may be.