I wonder if a significant part of it is down to family. People are not having large families these days, contenting themselves with only one or two children. This means an increased incidence of families where boys and girls grow up and socialise separately. Combine that with single-sex schools and less neighbourliness and you have an increasing disconnect between the sexes. Further, both parents are often working so hard and so long they have less time to be positive role models.
i can only comment on our experience however i tick a few of the above boxes. (though the 1 child is through choice.... for most of my life i never wanted any!)
both my wife and i earn similar wages. with no major bread winner we split pat/maternity leave - she had 6 months i had 3 - luckily both our works were fine with it.
we only have 1 child but both need to work... however i absolutely contest that children with working parents lack role models argument (or that they have to lack role models). unfortunatley neither sets of our parents can childcare much - my family are 200 miles away) but after school clubs which we use 3 days a week are amazing. they are run by teaching assistents, and whilst it is all play stuff, it is with either an educational slant or a physical educational slant.
our lad is 6.5 but he gets to mix with a range of ages of kids from 4 up to 11 and i think this is great for his developemnt. he is doing well in school (i am more worried about personality than other stuff right now, tho he is fine educationally as well esp if we help). but the thing which proves to me it is a good place for him is that when me or his mum go to pick him up he rarely wants to leave.
he has been in holiday club this school hols for probably half of the days he is off (family holiday mixed in) and they have had cooking days, sports days, water fight days, every day has a special theme. it isnt amazingly cheap but not extortionate either (just under £30 a day but paid with pre tax earnings so its less than that) but i think it is brilliant, better than what a lot of kids get when at home imo.
for the days when he isnt there of course the onus is then on us to do family time together, but maybe because it is more limited we work harder at it.
when i was a kid my mum was full time stay at hom mum (then she got a job as dinner lady at my school). maybe i am kidding myself to stop my own guilt but i honestly think our lad has just as much attention and mixing as i had.
Us both having to work is simply a necessity in the modern world i am afraid.
i guess one of us could become a full time career but then we would all lose out.