Eventually we may well simplify the world to the bare essentials, and it will still support billions more people.
The natural services humans actually need to fuel modern living come from microbes of decay, a few main insect pollinators, the ocean’s photosynthesizing plankton, and non-living things like water and the atmosphere. Eventually we may well simplify the world to the bare essentials, and it will still support billions more people. Indeed, that’s the only way it can.