Consumption. "Economic growth" relies on always increasing consumption. I am not saying that we should stop economic growth, but we might want to learn do it without bringing new consumers into the world, at least not making this obligatory.
That cannot possibly be true. A single person can consume a huge amount of resources - far more than any of us currently does. For example, by setting a building on fire, you have consumed that building. We already have a near-infinite capacity for consumption.
Or did you mean something different? If so, could you please explain it better? How can economic growth rely on increasing consumption? Because I would love to consume a yacht - where do I sign up to help economic growth by consuming one?
I'm looking for those who assert it is a good thing. You said "we might want to learn do it without bringing new consumers into the world" which to me suggests it is not a good thing.
If there are more people, it's fine, we should engineer the way to accomodating them without damaging the environment too much.
If there are less people being born, this is also fine, as human population is sort of self-regulating in this regard. Perhaps there is also some engineering needed to adjust for this scenario as well.
But neither growth nor decline are to be regulated in any way.