Larger populations both enable and incentivize more R&D, art, etc resulting in net positives in the short and long term. That’s somewhat counterbalanced by smaller global population having more resources per person to work with, but you have fewer geniuses with 0.8B people vs 8B people.

The speed of population collapse also impacts our ability to care for infrastructure and the elderly. While I personally think the global population would be better off at a steady 2-5 Billion people vs 10-20 Billion, dropping down to say 100M would make modern electrons manufacturing difficult to maintain let alone improve upon.