The struggle for resources doesn't stop if everyone becomes feminized and lays down their arms. It just means both waring tribes die. I'm sure the world you want has been attempted and failed many times over.

One of the reasons so many women have become so pro-transgenderism (besides the fact that they have never played sports) is the "Women are Wonderful" bias, or the idea that male behavior/muscularity is something that needs to be purged from society.

In that way, the hard anti-male Spinsters are really in the same boat of the pro-transgerder people they rally against without realizing it.