I don't think there's any expectation that humans will go extinct. We're here to stay. Suggesting this is about the extinction of the human race is a strawman.

The question is each of us needs to answer around having kids is firstly about whether or not you want to raise them in the world we live in, and secondly about whether you want (or care) that your children live in a world where the climate is broken, and having to deal with the resource issues, heat, wars over liveable land, etc. Heck, I'm sure plenty of people on HN are under 30 - there's every chance that they'll be around to see these problems first hand.

People who do want to have children are arguably very fortunate that there are lots of people who don't. The children who are born with have to deal with less contention for resources. That said though, they're still in for a pretty bad time by all accounts. Even if technology magically fixes everything, you still have to wonder if your kids will be in the part of society that can afford it.

But that is the root of the climate crisis. When it was just 150M Americans living a developed-world lifestyle, the climate was fine. As soon as you broaden that out to the 8B+ people living today, allowing all the folks in China/India/Africa to have the same lifestyle as the West, you have problems. In 1960 the average American emitted 16 metric tons of CO2; China emitted 0.5 metric tons and India 0.2. In 2020 US emissions actually decreased to 13.8, but China is at 9.2. Per capita emissions can decrease modestly but if you increase the number of capita by 50x, total CO2 emissions will increase accordingly.

Likewise, the climate crisis is far more likely to be solved by WW3 reducing the population down to ~1B than by individual per capita reductions.