It isn't crazy. The system we have now is crazy. The fact that we're mentioning artificial wombs instead of destroying capitalism is worrying.
To a certain extent, it seems to me that very generous benefits for parents -- _or_ a total restructuring of retirement and pension plans, with the reinvestment of some of the gains in pro-natal policies -- is "getting rid of the aspects of capitalism which make it too difficult to have kids." Or at least side-stepping those aspects. And these policies should be not impossible to implement. "Destroying capitalism" on the other hand...
If I was to encapsulate it in one word: pressure. Or insecurity. Pressure to work, pressure to make "sound" financial decisions, of which committing to a dependent is not "sound".
There should be options available to do nothing. We have private companies extracting "stuff" from the ground and privatizing the resulting profits. This is crazy. We throw out something like 1/2 of all food, which on average comes from hundreds of miles away so that food costs money, which if you don't have you starve.
We subsidize farms, the military, all kinds of things - but we privatize the profits.
There should be no threat of homelessness or starvation in our system. You want more than baseline, you have to work and compete. But we spend all this money to prop up this shitty system, I do not understand it.
So there are two options left on the table, which are bad but not utterly unreasonable:
1. Huge cash payouts for parents of children coupled with extremely generous incentives, both far beyond anything offered today. e.g., a $100k to $200k grant per child upon birth, with all hospital fees associated with childbirth covered by the state, free access to government childcare, and extremely generous tax credits for parents.
This might result in the wrong "sort of people" giving birth to many children... but at this point it's the one thing that hasn't been tried, it would resolve the concerns you mention in your post in a totally general sense, and it could also be a way to raise underclasses from poverty.
2. Manage the decline by investing in industries that can support an aging population, in programs that aim to pull people from decaying small towns into regional hubs, and by renormalizing retirement and pension schemes.
If there's a third way that isn't crazy -- which is to say bad _and_ unreasonable -- I'd like to hear it. (Examples of crazy ideas might include buying newborns from parents and raising them in government institutions, breeding children in artificial wombs, totally unfettered mass-immigration schemes, etc.)