"We at least now know that population peaks with prosperity, and food is largely a solved problem."
Solved problem for now. A large part of world's agriculture is dependent on stable rainfalls and temperatures. If climate change gets bad enough, a big collapse in world's food production capability might happen.
"Solved problem for now." With "now" being the important word here.
We should not forget the significant amount of soil erosion. Not only, but especially in already vulnerable regions. While I will probably not get to feel it, the next generation will.
There are quite relevant studies already showing how the erosion of soil is already impacting agricultural yields. And that it is likely only getting worse from here on out.