I really think women should leave if the relationship is abusive.
But what about if it's not abusive it's just not equal? And who gets to decide what 'equal' is? It's quite possible two partners would have different views on that.
Long-term relationships do require some compromise and concession from both parties. If you don't have that, it won't last. And if you're waiting for a relationship where everything is your way all the time, then if you do end up in it, it's likely the other person will be the one doing all the compromising.
I don't think it's possible to generalise so massively. It sounds like OP's relationship was unhappy and so she made the decision to leave. Others make the decision to stay. Presumably they make that decision because, overall, it's not so terrible or the alternatives are demonstrably worse.
Yes, being in an unhappy relationship is bad for the kids, but marriage breakups and having to live at two homes and having separated parents who don't like each other is also difficult for children. Pretending one option is always best in all situations is just not realistic. Abusive relationships are different, but this does not seem to be what we're discussing here.
I think what would be helpful would be to try and educate boys that they should be doing equal amounts of housework and childcare and to try and get rid of the destructive stereotypes that lead some men into assuming that women should do the lion's share of housework and childcare even if working full time and that they enjoy it. And destroy the idea that women and girls are 'lesser' than males.
And also really put laws in place that protect women when they've had children. I was made redundant after my first child whilst on maternity leave, this is common, it's not easy to fight particularly if you've just had a baby, your health isn't good, and the company claims they're completely getting rid of your job. it's one of these areas where IN THEORY it's illegal to do this but in practice it's common. Many women fall back on their husband's salary if this happens, I did. Of course I did, what else was I going to do? It did mean my career was destroyed but that wasn't DH's decision. It wasn't his fault that shortly after redundancy he got offered an amazing job abroad on higher pay and we decided that - in our family's best interest (but not really mine) - we should accept. Life is a bit random at times, and because of systemic bias mothers are often on the losing end of these things.
Support services are also inadequate for single mothers and women leaving relationships with insufficient finances. Many women ending up homeless or sofa surfing. In terms of abusive relationships: the courts often enable ongoing abuse of children by fathers - and mandate the mothers to hand over their children to a man they know is abusive for long periods of time, who may continue to abuse and / or neglect the children and it's very difficult to change this. All this needs fixing so it's easier for women to leave.
@ZeldaFighter has described I think a very common trajectory for a lot of marriages. Children put a strain on marriages, unless you're very wealthy and can afford nannies. Of course they do. Expecting anything else is ridiculous and it sounds like Zelda's relationship has recovered from this period. So it wasn't a 'slippery slope' - it was a period where things were difficult, now things are better. If she'd left, she'd have never found that out.
I absolutely support every woman who wants to leave and better support for women in abusive relationships to leave. I also support women who want to stay and try and make their relationships better and more equal, even if the husband doesn't do enough housework or mental load or childcare.
It is good to have conversations about what equality looks like, but we also have to respect that not everyone will make the same decisions as we will and we can't possibly know the details of why.