The "overpopulation" people are essentially the most disingenuous concern trolls of the modern epoch. Since every problem can be expressed as a "per capita" value, its very easy to claim that less people would obviously fix whatever problem you're talking about (despite it not changing the facts on the ground: i.e. CO2 emitting power generation would continue to warm the planet whether it supplies 5 billion people or 10 billion - whether it happens now or in 100 years, mankind winds up just as screwed).

You then of course get the people who don't actually get that every generation is...well a new generation. For as many displaced and orphaned children as their are, there is not nearly enough for everyone who wants to raise a child to have one (nor any practical way to fix the logistics of that process, even before we get to biological imperatives).

And of course finally you have the reality that none of the people who ever bring this up seem to actually be aware of any of the statistics surrounding it: i.e. most western nations are at or below replacement level, so any population increase comes from migration. Birth rates are also falling in the 3rd world[1] - and this is principally attributed to success in fighting poverty, promoting women's rights and education, as well as family planning work. It turns out population management is easy - it's so easy that we've succeeded at it without even really trying.

Which leads to - as you note - the utterly shitty rhetoric everytime there's a breakthrough in reproductive healthcare. A whole little army of childless 20-year olds who feel entitled to pass judgement on people experiencing reproductive trouble, who want a child, and are going to have...you know, on average 2 children maybe because they're still accessing a high tech medical service.

[1] https://www.visualcapitalist.com/cp/charted-rapid-decline-of...