I think we don’t really need or want a huge human population. I am not suggesting anything drastic be done but more along the lines of what is the goal of human civilization? How many people does it take to attain that goal?
For example, lets say we have a generally agreed upon goal to learn as much as possible about our place in the universe. should we really expand to colonize the stars and spread humans throughout the galaxy and universe? What is the point?
I suggest we don’t really need billions of humans on earth to accomplish this. Perhaps only a few tens of millions would suffice. population growth seems to abate somewhat in educated cultures. already Japan has a negative birthrate. the only reason the USA has a positive one is due to immigration.
Why keep abusing the planet, Gaia, with increasing numbers of humans if a smaller number will be better?