I think this kind of thing is weirdly forgetful about the past.
Women have always worked - particularly in working-class households, agricultural and industrial settings in the past. Childcare was more often grandparents or older siblings and I fail to see why that was necessarily better than a nursery or childminder with training and regulation. Let's not forget that in the past children were routinely beaten and neglected and if they were abused, there was little help for them.
There have always been single parents too - longer ago, people died young / in childbirth much more often and single-parent families and stepfamilies were common - there are stepfamilies in loads of fairytales aren't there - I read somewhere recently that the levels today are similar to in the 15th century for example.
I would like to know how they know that children are less happy now. Could it just be that people listen to children now and we have much more concern for children with problems, so we know more about how they feel?
The sexism also riles me - totally unnecessary, what a wasted opportunity to put the focus on parents not mothers.
I do take their point about indivualism and consumerism etc. But they could have looked at the way these things might affect children independently of those other issues.
Totally agree about working hours too - and inflexibility and bullying by employers who put parents to the test by expecting them to work long hours, instead of making life easier for them.