I definitely get where you’re coming from, but I think population reduction comes naturally from things like abortion rights, good family planning provisions, and a lack of poverty. Countries with those things are seeing a decline in population without making having children into a moral issue.

Extra point is that, although the population is up, the amount of meat eaten is waaay up. Just looking at that one issue, we can solve over fishing pretty easily without requiring any change to the current population numbers.