Earlier quoted context omitted.
There are more fundamental questions here of whether we want population growth. There seems to be a de-facto equilibrium springing up where wealthy countries quietly drop below replacement rate fertility and then migration from poorer regions happens. It isn't immediately clear why this is a bad thing either. It seems intuitively fair, sustainable for the forseeable future, nobody is being forced to do anything again…
It causes lots of problems because many of our systems have been set up in times of growth and won't function without it. Take for example "pay-as-you-go" pension systems in much of Europe. Here, you don't fund your own retirement, but the current working population funds the retirement of the current retirement population. This works great when you have population growth, because you can have e.g. five working peopl…
Money by itself is worthless if you can't exchange it for actually useful goods and services. So non-"pay-as-you-go" pensions cannot circumvent demography, either – if too many retirees with their accumulated capital would be chasing too little working-age people providing goods and services, you'd just get inflation and all your accumulated capital became worth less.