Sure, I'm happy to oblige. I agree with your assessment that a solution won't come from economic policies alone, and will go so far as to put forth that there isn't a solution in an environment with free will (which will become evident later in this comment). With that said, economics are a critical component for successfully raising a healthy child to adulthood.
My research started when I had a fascination about population as a system, and how sub systems (each country and its ongoing demographics transition, Japan being the future of all developed countries, Israel being an outlier due to their ultra orthodox population) function within the system as a whole. During this research, I came across Hans Rosling's talks (mostly on TED, but other places as well) on population and growth, which led me to Our World In Data's extensive blogpost on the topic [1]. I will draw your attention to the section "What explains the change in the number of children women have?" [2]. What does this section tell us?
It tells us that when women have access to contraceptives/family planning services and are empowered economically and socially, they have children later in life, as well as less children than they otherwise would've had (or no children at all). You can also see this in data with regards to the growing childfree movement; the economics alone aren't a factor, these people simply do not want to be exposed to the opportunity cost or experience of having children [3] [4] [5], and there is some data that childfree unmarried women are the happiest demographic [6] [7]. Europe and Scandinavian countries that have much more robust pro-natalist polices than countries such as the US have close to parity or lower birth rates. Also, something to note is fathers having a lower fertility desire when parental leave is expanded to cover them at the same level of women [8]. In short, kids were an advantage when countries were developing, but in a developed world, they are a luxury good at best and a burden at worst.
Admittedly, my comment you replied to is only part of the problem: the fact that having a child in most of the world (outside parts of the developed world with broad positive economic outcomes for the middle class) is a poor economic choice. I didn't touch on the 400k existing children in foster care who have no permanent home in the US, the millions worldwide who live in institutional care, and so on. There are already large cohorts of children without a permanent loving home.
High level, I take issue with people advocating for a higher birth rate when we don't take care of the kids (and also adults, by way of social safety nets, affordable housing, healthcare) who exist today, and there’s substantial data that there are cohorts who just have no interest or desire in having kids regardless of what you throw at them. Fix existing socioeconomic systems and then calls for heroic measures to increase the fertility rate might not be so tone deaf.
Tangentially, the "out of touchness" I referred to isn't limited to just the wealthy and technolibertarians of course; the pope is equally culpable:
> Pope Francis decried the low birth rate in Western countries on Thursday, describing it as an urgent social emergency and a “new poverty.”
> “This is a new poverty that scares me,” the Pope commented. “It is the generative poverty of those who discount the desire for happiness in their hearts, of those who resign themselves to watering down their greatest aspirations, of those who settle for little and stop hoping big.” [9]
New poverty! We haven't even gotten past existing poverty and suffering. Maybe he should be scared of current state before arguing for more of the same.
[1] https://ourworldindata.org/fertility-rates/
[2] https://ourworldindata.org/fertility-rate#what-explains-the-...
[3] https://www.pewresearch.org/fact-tank/2021/11/19/growing-sha...
[4] https://journals.plos.org/plosone/article?id=10.1371/journal...
[5] https://ifstudies.org/blog/the-rise-of-childless-america
[6] https://www.businessinsider.com/unmarried-childless-women-ar...
[7] https://www.psychologytoday.com/us/blog/why-bad-looks-good/2...
[8] https://www.theguardian.com/world/2019/may/20/paid-paternity...
[9] https://www.ncregister.com/cna/pope-francis-low-birth-rate-i...