Good! Planet is overpopulated relative to how much we damage the planet. Current population growth rates are not sustainable long term without massive technological improvements, and it's not worth the risk to assume that those improvements will happen.
On the other hand,
Uh oh! This is happening for all the wrong reasons. It's not enlightened decision making. It's just too damn expensive(both time and monetary cost) to have kids.
I don't know, we'd probably have to measure the carbon footprint per capita and see what it would take to be net neutral I suppose. Which would seem like a population of 0 based on our current carbon output.
Obviously that's very morbid. And I like the idea of improving ourselves to be more sustainable. Population decline seems like one way to go to preserve and protect the planet from human destruction, but like you said, people are amazing, and I don't doubt that we could figure this out.
There's a great book on this called the wizard and the prophet. Might be worth a read if you want to know more.
My personal take is that the risks of high population growth are insanely huge. Science and tech are great. They are far and away the best ways to produce value. But assuming that there will be magical solutions to every problem we are creating is wildly irresponsible, and is part of what has led to this slowdown in population growth. Fishing is harder because we killed most fish and now the price of fish is increasing. We are largely as developed as we are due to natural resource extraction. Fish populations fed early humans but are down massively compared to pre human levels. Almost every single old growth forest is gone. Many species are extinct. There are lines which, when crossed, take millennia or more to recover from. We take way too much for granted. Full speed ahead would likely result in an overpopulation crisis. Give predator prey ecosystem graphs a google. Give Kesler syndrome a google. Give superintelligence by Nick Bostrom a google. We need to slow down actions which may have long term impacts across the board. More thinking, less doing.
Sorry for sounding so scary and dark. It's hard to talk about extential risks without seeming scary. I'm nice in person I swear lol!
I'm in the camp currently that quality can trump quantity. We can have fewer people but improve living standards through automation and education. Not only that, fewer people means less competition for doing those kinds of amazing things you mentioned.