I'm not sure I completely agree with the economic argument, particularly because birth rates and wealthiness tend to move in opposite directions and because a comparative analysis doesn't show that strong welfare states which protect a person's income, income stability and alleviate all the costs of being a parent, don't show strong birth rates either. It feels like getting children is still very much a choice, but that our cultural norms about what a 'proper life' means has changed. No longer as a young person do I feel as compelled to marry, get a home in a suburb with a yard and a dog not to be cast out or judged. It's not because it's more difficult for me to afford kids than my parents or their parents, who struggled financially more than I do and had to work more hours, had less leisure time, fewer luxuries etc. I think it's a bit too easy to say 'kids these days saw parent' savings disappear in the financial crisis' as if their parents' parents didn't see their parents in world war ii, and their grandparents in the great depression as a reason not to have kids. Again, wealth and birth rates move in opposite directions. Kids used to be a form of welfare system, too, you had no state or business to give you a pension or pay for your care, but your kids did. Now we're rich enough where kids aren't needed as an economic asset (working the land) or welfare asset (caring for you in retirement). But to say they're less affordable than before, I'm not so sure.
Most of the predictions about the welfare state are true, though. In that some of its effects mimic a ponzi scheme.
I'd urge everyone and anyone to look up an age pyramid for their country from 1950 and onwards. It's absolutely telling. Preferably an animation.
e.g. Japan here: https://www.populationpyramid.net/japan/1950/
You can click through every 5 years. It's like a snake with food passing through it's body, starting with a big blob of young people who gradually move into old age, without replacement. The proportion of young (suppose an arbitrary =40) to old completely flips over. In Japan it was 75% in 1950, but just 44.5% in 2010. If you take 65+ as a threshold, it was just 5% in 1950, but 23% in 2010. That's 4x as many retirees to support on a dwindling young (mostly) working population. 5% 65+ and 95 And that matters a ton because there's a gigantic age asymmetry in terms of expenditure by age group in certain fields. Take healthcare expenses by age: https://jamanetwork.com/data/Journals/JAMA/935941/joi160128f...
You basically spend a ton at birth and as an old person. With low birth rates and massive improvements to healthcare increasing life expectancy, we're heading for a disaster. The tax base is rapidly depleting and the tax burden is rapidly increasing.