But I'm somewhat sympathetic to this argument. While there are certainly more people in absolute numbers living in poverty than there were 2000 years ago, the percentage of people in bad shape is probably lower. And many versions of "bad shape" today is probably still a lot better than the average at many points in history.
That leads to a philosophical argument, though: is it better to have more people, with a higher proportion that are happy and doing well, or to have fewer people, with a higher proportion that hare unhappy and doing poorly, if in the second case, the absolute number of people in bad shape is fewer? I think it's reasonable to disagree on which is better; there's no objective truth there.
I think the argument is that the marginal utility/productivity of a person > the resources it costs to sustain a body, even if that body is minimally productive (i.e. subsistence farmer). I think we're better off trying to improve ratio of estimated 2B subsistence farmers that can be replaced with (generously) 100m farmers + machines, and try to figure out how to improve productivity of rest. IMO there are still so many existing poor people, and for purpose of this argument, non/under-consumers, that there's ample (billions of low HDI/low productive workers globally) of untapped demand that can be uplifted to drive growth in all the big things this article calls for. The argument would be different if global human capita productivity is already optimized/maximized and adding more bodies is the only way to raise ceiling, but we're not even close.
Current world isn't good enough for everyone.