I cannot say I agree, and I think I recall that some indicators currently suggest we'd need about 3 planets to keep going at the same pace.

The back of the envelope calculation says if everybody on Earth lived like an average American we'd need the resources of about four Earths to cover it:

https://www.bbc.com/news/magazine-33133712

That being said, from the same source, if everyone on Earth lived like an average Indian we'd only use half the Earth's resources and could support twice as many people.

So it's not about the number of people - it's about the standard of living those people have and the resources they use.

I think the most effective way forward is more efficient and sustainable lifeways - if the richest countries learn to consume less, if people around the world get access to better technology and better institutions to raise their standard of living without raising their resource consumption.

And it's interesting to note, the better off people are, the fewer children they tend to have. If we improve people's lives worldwide, a steadily declining population will be a natural side effect.

An incredibly difficult goal, of course, but worth pursuing.