Birthrates at or below replacement rate are ultimately a good thing as we improve automation and AI. Infinite population growth is not a realistic model. We can't even prove the current population level is sustainable.

> We can't even prove the current population level is sustainable.

Everyday we prove it slightly more. To exhaust the nutrients in all the mud in the world would take a lot more farming, but we thought that ip4 addresses would never run out either, so maybe it will happen.