The Peripheral The biggest problem for me, is after the catastrophe, and collapse of everything, the survivors have "won the lottery". But the book never really explains how this future turned out 'good' for the survivors and not a 'mad max' like dystopia like every other post apocalypse story. If there was massive population decline, then how are they making all that technology? Is it all robots? Who built the robot…
Natural resources are still the primary constraint on human prosperity: food, energy, land, metals, ect. In a depopulated world, the average persons labor is the same, but they are working with only the best inputs. You might have the same number of fishermen per capita, but they are fishing the best 1% of fishing grounds without competition. If you drill for oil, it is now in the top 1% in terms of ease of extraction. If you build a dam for power, you have more site capacity per capita. If China had 1% the population, the three gorges dam would supply enough power for entire country two times over.
People learn about economies of scale and high school econ, but there are also ineconomies of scale. At some point there is no more efficiency and gain from increasing the size of your widget factory. However, it might be more expensive to import power and metal from further and further away