One-child / two-child policy was the real centrism all along.

No, that's bad too, and it arguably didn't even work. You can look at the start of the one-child policy in China and similar population control policies the U.S. essentially forced on India, and it took about a decade after their implementation to see population growth rates start to drop.

What does work to reduce population growth -- voluntarily -- is giving women rights, education, economic independence, etc. Turns out when women have a meaningful choice in the matter they usually have fewer kids.