I think you’re absolutely right here. I’ve noticed that there’s already an analogous concept to “toxic masculinity” for women, which is “internalized misogyny”. An example of internalized misogyny is when women believe they have to be rail-thin to be properly feminine or attractive.
I’ve never understood why this isn’t called toxic femininity. If society’s standards of femininity cause women to become anorexic, that standard of femininity is clearly toxic. Just like how a standard of masculinity that causes men to take steroids and damage their bodies would rightly be considered toxic by everyone.
I think the reason is that there’s a kind of cat-coupling. When you say “I visited the famous golden gate bridge”, you don’t mean “among all the golden gate bridges, I visited the one that was famous”. You mean “I visited the golden gate bridge, and by the way the golden gate bridge is famous”.
When you say “toxic masculinity” even if you mean “the subset of masculinity which is toxic”, it’s possible to interpret that as “masculinity, and by the way masculinity is toxic”.
Feminist academics, being mostly female, have no emotional response to the idea that saying all masculinity is toxic, so the possible misinterpretation doesn’t bother them. But they might have a response to someone saying all femininity is toxic, so they wisely chose a term that was less likely to be misinterpreted (“internalized misogyny”). More diversity in their field would have prevented them from making the same mistake w.r.t. toxic masculinity.