Agreed. By just about every measure, we're much better off than the past, yet have fewer kids. Statistics have supported this correlation (richer -> fewer kids) for a century, across the board around the worldwide, yet people often still get the causality exactly backwards: it's too expensive to have kids.
Real median incomes have risen, decade after decade.
And because of this, consumption in key categories has improved. For example:
Housing floor space per person, same trend.
Life expectancy, same trend.
Leisure has increased.
Tourism has increased.
Yet the common discussion is that it is unaffordable or impossible to have kids. It's backwards. My grandparents were dirt poor and each came from families with 8-10 people. I'm comparatively very rich and have no kids. The explanation that it's so unaffordable I think is mostly wrong. It's that not having kids for many people is a better deal than before.
The cost of kids isn't unaffordable per se, but rather opportunity cost is too high.
As an example I just came back from travelling the world for six months. I'm rich enough to do that. Which also means the opportunity cost is so great, that it's a lot to sacrifice to have kids. My grandparents had none of that opportunity cost precisely because they weren't rich.