Honestly, we need to reform our economic system and not continually rely on fertility to solve all of our problems.

Fertility and demographic collapse aren’t about supporting an economic system. Even if we were a post-scarcity communist utopia women would need to average 2.1 children/woman to maintain the existing population (2.1 isn’t growth, it’s maintenance - if you wonder why it’s slightly higher than the number of people involved with making new people it’s because you also have to cover for infertility and mortality among those children) or the same population-level result would occur. The nasty thing about demographic collapse is that it’s subtle until it isn’t and by that point it’s really hard to fix. There is no economic system where people don’t need to make more people to have a stable population, at least not unless/until we achieve some kind of immortality.

Ultimately you have three options when it comes to the topic, and they all have downsides:

1. Get your people to make more people. Downsides: Those new people aren’t really contributing to society for a couple of decades, which means it’s a long term fix for a problem that might be a big problem in a shorter term than that depending on where we’re talking about. Also, there aren’t a lot of ethical ways to do this, and the ones that are ethical aren’t extremely effective.

2. Import people from elsewhere. Downside: If you do this too quickly and/or without pushing for assimilation you will irrevocably change if not destroy your culture. This is why places like Japan and South Korea aren’t allowing unlimited mass immigration from anywhere people are willing to come from despite being on the cusp of the “until it isn’t” part of “subtle until it isn’t.”

3. Do nothing, and hope it just fixes itself. Downside: This is essentially a death spiral for your people.