I didn’t make the claim that population is the biggest problem. I responded to the incorrect suggestion that population size is not a problem (which you repeat without offering any evidence that we could sustain ourselves). Growth is by no means a “solved” problem. Growth is expected to slow, but even at our current population size we are consuming an unsustainable amount of resources. And growth will slow as a result of increased wealth > higher consumption. Given that we live within the finite ecosystem of of our planet, this means we need to make significant changes and we need to make them now.