The thing is, the best athletes frequently have genetic privilege that others don't have, whether it be extra long or extra short limbs, being extra tall, having higher than average testosterone levels, etc. There is no level playing field.
I don't know what the best answer is, but what we are seeing now is pretty ugly.
In most cases though it's very obvious when a male is in a women's event. For example, no-one is going to mistake this male, who competes in women's cycling, for female: https://i.ibb.co/N6ZBzh4K/F4-Svyxt-XYAAMpc-M.jpg
The best athletes often do have some sort of genetic privilege, that is true. But look at the world records of pretty much any sport and compare the most elite male athletes with the most elite female athletes: the difference is massive. Even having advantages in limb length, lung capacity, and so on doesn't overcome the physical advantage of male development.
At this point it's hundreds of male athletes competing in women's and girls' sport: https://shewon.org/males