"Long term, the people born each year are children of people who decided to have kids". If there's far fewer parents because this cohort of potential parents i

"Long term, the people born each year are children of people who decided to have kids". If there's far fewer parents because this cohort of potential parents is much smaller, then you have necessarily fewer children going forward. Even if you double the number of people that want kids, it becomes very hard to reverse the demographic decline, let alone grow your society. Even if you could, there's still a giant demographic hole in your population that will cause big issues over time. Outside of immigration (which is a big discussion on its own) PLUS a healthy birth rate among these immigrants, I'm unsure where your optimism comes from for them reversing their demographics and growing.