I’m not advocating human extinction, nor even a return to some (fictional) 17th century agrarian Utopia. But I think there might be a sustainable, tech oriented, post-scarcity future that could exist.
Asking how we might get there actually ought to be the first question.
In short: People don't feel the world is worth bringing children into anymore, it's likely educating women doesn't help, and the relative economic precarity young people live in makes it seem extremely irresponsible. Then on top of all of that most developed countries have focused on individual consumption and hedonism rather than evolving older social traditions that tended to encourage family formation so younger people don't even have the psychosocial tools to dig themselves out.
It just now occurred to me that maybe uneducated women get married and have kids out of economic self-preservation. The more educated, the more able to make their own way, the less they have to marry and have kids if they don't want to.
But maybe we're also in an over-reaction. Women felt stifled in that environment. So they got jobs and bosses and all the workplace stuff that we find... stifling. It's not necessarily better; it's just a different flavor of bad. As more women have time to try it and find it to be empty, we may see a reaction away from that as the ideal of what female success looks like.
Women have always been able to work, there are plenty of low-education jobs available and the poorer they are, the more of those they need to get shifts for. You may notice women working in many crap jobs when you look around. Higher education changes the jobs generally for the better. Also exposes them to "hey, there are more things going on in the world besides squeezing out babies". Though the educated who like making babies can and do go right ahead.
The primary reason this is a problem is due to the need to support an aging and/or non-working population via the next generation. Too few working compared to non-working can't support the system.
Generally the birthrate to keep things in balance is approx 2 kids per couple.
If anything, drive fertility rates lower faster through robust empowerment of women. As the labor supply compresses over time, labor will have more power as demand exceeds supply. Unwanted children? Solved. Systems that don’t provide for those in need? Less effort needed to force those systems to change. Everyone wins except extractionists.
I don't want to live in the 1920s, or worse, the 1820s. Can the population shrink, and we still maintain our level of tech (and even maintain some progress)? How far can the population shrink, and we maintain that?
I can tell you that I live in a country with a population well under 10% of the US', and memories of WWII giving us pretensions towards autarky, yet we still do cutting edge research, and most tourists consider the local standard of living reasonably high.
(in particular, we do not rely upon —as in my memories of the US last century— having pools of day labourers standing around waiting at "the wall" to be at your beck and call for all your low-productivity economic needs)
Are you advocating for quality of life and consumer excess over human suffering?