I'm also an early millenial / late GenX and broadly support the things you mention.
At the same time, how do you explain that earlier generations were happy to start families well before national pharma care, etc.? Before people were concerned with the climate crisis they were terrified of a population explosion (hence China's one-child policy), nuclear war, etc.
My intuition is that the difference is that they were more financially stable and they were able to maintain a family with a single income, which provided them with both the money and the time that raising children require. So, maybe we should focus on that instead.
Developed countries have fewer children than necessary to maintain their population. If overpopulation is your concern, you have to look elsewhere, and the measures you need to prevent it will be different.