I find this "solution" very problematic and stupid. There is no way to separate economic progress from labor because economic progress is directly tied to labor. Your proposal of reducing birth rates as a solution is Malthusian nonsense. The problem isn't the amount of people there are on earth, it's capitalism that exploit and oppress those people. There could be 500,000 people, but if those people continue to live in an exploitative system, their suffering will still continue.