That is not happening, as societies get richer and more stable overall, people just stop wanting to have that many kids. In Europe this has been happening for like 40 or 50 years. The internet or "the promotion of dumb behavior" has nothing to do with it. I mean you either are so poor that you need extra kids as a work force, or you are rich enough that having kids stops being a financial and emotional burden. If you are in between (read "almost everyone in advanced economies"), you just aren't going to have that many kids. The fact of the matter is that the entrance of women into the work force has not increased families purchasing power as much as it should, especially considering that during the 20th century in advanced economies, kids went from being potential family income to dead weights (this is a good thing, in case you are wondering).
People aren't having kids later because feminism is promoting it. People are leaving their parents' houses later and later because they can't afford it, they aren't having kids earlier because they can't afford it, and they aren't having more kids because they can't afford it. Real wages haven't kept pace with the growth of advanced economies in the past 50 years. That's it. If you want people to have more kids they have to make more money. Big companies across the board are making loads and loads more money every year, but that money isn't entering the economy in a real way.
The Swedish government has been promoting having more kids for years, by the way. More money paid to families with more kids, more time at home with newborns, free child dental care, free college. Anecdotally, I can say that upper middle class families appear have more kids now. It is not uncommon for me to see 3+ kids families around. Still, they are not having 6+ kids, which I imagine would be necessary to offset all the families that have between 0 and 2 kids. There's only so much one can do if wages are low.
https://www.epi.org/publication/charting-wage-stagnation/