In the long term we are all dead. So we have to want to do these things for people who are not born yet and who will never pay us or pay us back or be able to even thank us. We have to do these things because these things are the right thing to do.
That will decrease our wealth.
Now please explain how capitalism can do that?
That's why I find a lot of the antinatalism of modern western culture to be concerning.
The net impact of having three kids has been a net positive for the environment and society, I believe.
I don't think that's required, or requires blaming antinatalism. I don't have children, but I recognize that others will, so I'm motivated to address long term problems for the sake of future lives.
There's also some cognitive dissonance in recognizing that the future world faces existential risks like climate change, but then choosing to have children (who will have to live under those risks!).
At two or three billion it would not be an issue at all.
We don't have to do anything. As women (e.g. in sub Saharan African countries) get more education, the age at which they have their first child increases. As expectations of having your own place increase, and rent increases, the age of having the first child increases. If you want to go all the way, look at Japan, with its aging population and young people who don't want to have sex. Many of them are shut-ins, hikkomori.
Even without this virus, we have been moving towards a world where everyone lives on their own, orders in, gets amazon deliveries, etc. Both parents work for corporations, kids are put into a glorified daycare center run by the government, everyone is overmedicated, from kids (ADHD) to adults (opioids and antidepressants) to elderly (nursing homes) and this is called "a good economy".
If we lowered the workweek to 30 hours, and implemented a permanent UBI (as Spain may do now, and Alaska has done for a while), we could have people spend more time with their families. And if we moved towards increased collaboration rather than competition, we would have a lot more value for the world (think wikipedia vs Britannica, Linux vs Windows, the Web vs AOL etc, Netscape vs IE (thanks for open sourcing that one btw :)) you get the point. Science vs Alchemy.
Anyway, the world has adjusted since we greatly reduced child mortality, and some countries are just playing catch-up. Eventually, we will have a smaller, richer population, with robots and automation doing a lot of the work. That's the future. The only trouble is, shortly after that we'll all live in a zoo controlled by AI :-/
Having kids doesn't make you wiser.
But it makes you more receptive to arguments about anything that could endanger their safety and future.
My wife has started to be much more environmentally conscious (vs. economically conscious) over the past year, and I think it all started due to one off-hand remark: I said that I hope our (then about-to-be-born) daughter will be able to experience snow. She brought up that particular phrase to me many times now; it seems it really stuck in her imagination.
On the other hand, people with children have less resources to invest and are generally forced economically to prefer today's consumption (eg. feeding, clothing, transporting, schooling their kids today instead of buying solar panel stocks for tomorrow).
I am not sure you want to involve yourself with those folks and this toxic ideology. It is not inevitable that every life liberated some huge sum of tons of carbon.