A society needs to have sufficient children born to each generation in order to self-sustain. Those without children, just like those with children, rely on the younger generations' economic contributions to support them. Those who can and does choose to have children, usually at a significant financial cost, are sholdering the burden.
I say this as someone who is child free, through choice.
However, decades of right wing economic policy has made having children extremely financially burdensome, as it has other life milestones.
My DP and I are in the top 5% for household income but neither of us come from well-off families, and we weren't able to buy our first house and car until our late 30s (albeit, we both had fairly prolonged studies, and loans to cover them, to obtain the qualifications that have given us good salaries and, of course, we had far more modest salaries towards the start of our careers). If we had decided to have children, a home would have felt unattainable.
Of course, the extent of financial pressures vary depending on where you live (for us, its Vancouver, which is at the extreme end for housing costs) but they're present for everyone.
Is it a morally good thing to have children (in light of current birth rate trends)? Absolutely. But the primary moral failing that is causing the birth rate crisis (and is starting to push some countries to the brink of demographic and societal collapse) is on those who have failed to address the disastrously-uncontrolled capitalism that has favored the mega-rich to the detriment of the majority of society.