I don't think it's depressive, and while I want to say it's atypical, I don't think it is - it's just more extreme and obvious with SEN and disability.
You're right that a, it's happening and b, they are winning. They have won. Because we won't do it. I probably personally could - DH would take on DS, no problem (apart from possible legal stuff since he's not his legal dad - but then who would look too hard if there were no women) but if he was younger, if I was still a single parent, if I was still with my ex, no way could I do it. It's a biological drive to protect your DC, it has to be.
I would think that most (and I mean 99% of) women are either in a situation where they have somebody that they absolutely would not leave under threat of death, or don't see the problem [at all, or] as anywhere near important enough to leave/strike over.
The problem is that when everybody sees it as women's responsibility to do these things - men/patriarchy/state see it as women's responsibility and rely on them, women see that nobody else is doing it and hence know it's on them, it's very hard to then say "Well no, actually, it is your responsibility too. Here, deal with it." Because if everyone thinks it's your responsibility, and you've accepted (reluctantly or not) that it's your responsibility and everyone's acting like it's your responsibility, hasn't that made it your responsibility? It's not just something you can randomly assign. Somebody has to take it. And we have. Even if we handed control over to men, everyone would go "Wow, women neglecting their responsibilities!", they wouldn't magically think "Oh hang on, this was supposed to be my responsibility all along too."