Modernity has seen more than ever people going to university as a rite of passage...even those who are not particularly academic..and as a consequence degrees have become somewhat devalued...plus now there are simply not enough degree level jobs to go around. And student loans now mean a life time of debt......if the young person ever gets a job which earns them enough to pay some of it off.
It is a hard fact of reality that a woman's most fertile years are in her late teens and twenties, and fertility rapidly goes off a cliff edge, just at the time when many women now feel they are in a position to have or want children. Added to that the ridiculous cost of housing....which now requires two full time adults in work to be able to afford. Women who do have children are having to spend a whole salary on nursery or child care ( ineviatbly it will be other women who look after their children or do the paid for domestic chores) because they cannot affiord to go P/T or even give up work for a few years.
It's all well and good talking about shared childcare responsibilities, but 9 times out of 10 that it is the women/mother who takes on most childcare responsibility ( for obvious reasons). I do see men pushing prams and pushchairs a lot more now than used to be the case, but you can guarantee it is still mainly women.
Having children is now presented as a burden - one that will ruin your life, stop you from doing what you want to do. People now live lives which are very much focused on travelling, eating out, socialising with friends...well into their thirties.....but the older you get the decision to start a family becomes a more difficult one to make. There never seems to be a good or a right time.
Men don't feel the pressure of the biological clock in the way that women do.....and many are more reluctant to settle down ( even though there are still men who very much want to have a family and children). People cohabiting is more normal now than it was...and marriage is seen as an unecessary piece of paper....everything is more transactional and provisional than ever before.
All of the above factors are shaped by social and cultural factors, by social trends and patterns...and if and when those patterns, expectations and trends change then most likely people will make different choices. Getting housing right....housing needs to be decent and affordable...and supporting mothers and the family with tax incentives etc should be a major priority.
Working from home has become more of a possibility now for those in desk type roles.....and this takes off some of the presure too, as well as providing some degree of flexibility.
Not having children because you are terrified of climate change is an unfortunate consequence of our times. Societies do need to have children, you cannot just rely on the children of peole from other countries and cultures to do all of the jobs that need to be done, and at the end of the day...we are sexed creatures and the purpose of of having two biological sexes is for reproduction.
Even those who consider themselves to be the best parents will find that their children hold them responsible for some harm or damage at some point. When children psychologically begin to separate from their parents they can be very critical and unforgiving.