Those things are true in the current climate regime. They may not hold true when global average temperatures exceed 1.5 degrees over preindustrial. In addition to decreased crop yields what we will be able to grow will be less nutritious, not even getting into increased mortality due to heat and other human impacts: https://climate.nasa.gov/news/2865/a-degree-of-concern-why-g...

Maybe, just maybe, we should ask questions about people who have 10-12 kids or something like that, but a replacement rate of 1-2 kids seems more or less unquestionable to me.

I mean, if you feel you don't want to bring kids into this turbulent, uncertain world, by all means don't, but please also recognize that one of life's biggest purposes is to beget life and we will do nothing (and have never done anything) if we didn't reproduce