The OP, tho, is about plain men being in a women's changing room, which is a natural result of saying that any man who do chooses is to be accepted as a woman. He doesn't have to go on any 'journey' at all because a huge proportion of the population has been brainwashed into not even questioning such a man.
I understand the point you are making, and agree (perhaps unsurprisingly) that it is dangerous. If anyone, male or female, can be a woman, and if it is virtually impossible to get anyone other than a gender-critical feminist to define what a woman actually is, then being a woman is meaningless - women are meaningless.
If there is nowhere that women can go that is not accessible to males, then women from separatist religions will lose freedoms. Women without such religious beliefs will also lose freedoms, if they feel uncomfortable about having men in places where they feel vulnerable. Men, on the other hand can go where they like, and women are expected to just let them in. It's not difficult to imagine that there will be men who enjoy having that power over women.
A man who has transitioned and sees himself as a woman is likely to be accepted and included in most day to day activities as a woman. In my experience, most women are very accommodating on a personal level, and will not make transwomen feel uncomfortable unless there behaviour warrants it. It is not 'genuine transwomen' who are the issue, though - it is the men in the OP.
The idea that we can't question the right of men to be in our spaces on pain of being accused of transphobia is insidious. What's next? That we can't question their right to touch us?