shoesandwine only female people can gestate a child, only a biological mother can breastfeed.
It's the woman, therefore, who is massively more impacted for around two years per child - because of human biology.
Pregnancy and childbirth have absolutely cataclysmic impacts on many women physically. Breastfeeding too, to a varying extent.
You might want to believe this can be shared 50/50, but it is simply not a physical possibility.
If a couple want and manage to have 3 children and have them singly, that's six years of a woman's life which absolutely is far more intimately, completely, and centrally impacted than that of her non gestating coparent, (even if they are a lesbian couple and only one can carry a pregnancy this would be the case, because of the biology of human reproduction, not because of gender roles).
If you've carried, birthed and breastfed a child you are highly likely to find being apart from that child while they are still tiny and wholey dependent for absolutely everything harder than even a very involved coparent at first. The bond is initially physical and biological.
Obviously as the baby grows into a small child parenting can become 50/50, but it's often the case that pregnancies, losses, breastfeeding, maternity leave impact on a mother's career more than a father's, especially where parents don't wish to have an only child.
Mothers are treated very differently to father's in many workplaces - father leaves early to pick his child up and gets a standing ovation, father of the year award and even mildly flirty comments about being the sort of man every woman wants to have children with. Woman leaves early to pick up her child - gets rolled eyes and snide comments about her crotch droppings not being her colleagues problem and how she's setting equality back and making women look bad. Who is overlooked for promotion due to divided loyalties... Super dad or flakey mum? Despite identical behaviour...
Comments about 50/50 parenting of babies can sound quite naive tbh. IMO it's an aim once children are 2 or 3+ but unrealistic before that.
Ideally IMO both parents would work part time - both parents working long full time hours is unavoidable for some couples but really, really not ideal at all for small (or arguably any) children.
If a couple aim for 50/50 parenting that's great but seriously difficult and requires both parents' employers to be exemplary. Worth getting set up before even TTC...
How many couples could really both go down to part time with consequent reduced income and reduced long term career progression?