Western societies are already down to around replacement levels with some going below it. It's pretty clear cut as societies evolve that population growth evens out. It's 3rd world countries driving the population growth. Over-population of humans being a danger to the earth has been proven false time and time again.
Overpopulation needs to be qualified with the context of the living standards. Ten billion vegetarians is probably feasible, but ten billion Americans (we don't currently have as many at such a standard) is a different story.
When some people stop procreating and educating the next generation, the world population does not simply go down. Instead it gets replaced by those who do continue multiplying.
The heritability of intelligence and other factors is highly variable.
You want people who will care diligently for their children to have them. Not people who will be largely indifferent to them, whether they're smart or dumb.
The Musk 'I'll have ten and scatter them to the wind with bags of money, the odds will take care of the rest' strategy is not really one that works out well in real life.
I'm the oldest of 11 kids, and I'd like to hear more of your thoughts on this. I agree with your second statement, which is why conscientious people should have kids.
Well, hello! I am also the oldest of 11 kids; I rarely encounter another like me.
One of the many reasons I have carefully avoided making any children over the years is that I already had my fill of child-rearing by the time I left home, through looking after my younger siblings. I wonder what your experience with this was.
There are no signs that intelligent people are not procreating. More affluent countries are not procreating, but that does not correlate with intelligence.
I'm all for having as many children as you can raise, and caring about old people, but interpret the following how you wish. It is a highly anomalous thing in the history that ordinary people receive real medical care when they are unable to do basic tasks themselves. You might have some basic care if your children care about you, but that's about it, and that might be our future and there's very little we can do about it except enabling policies that make having children viable option for those who want to have children.
Only 5% of people work in agriculture and 15% in industry. So we could reduce the workforce by 80% if only people would groom their own dogs themselves and just die when their time comes.
And if not healthcare is another 15%. But you probably can shave off a little from all those numbers if you exclude the time devoted to desperately trying to sell things to each other in the economy of abundance.