Fertility drop is a self correcting problem. The people who are not having kids will be less represented in the future gene pool. Those who are having 3 or 4+ kids, and whatever the associated genes are, will make up the majority within a few generations.

And also, humans probably overshot on reproduction in the 20th century. It was 5-10x growth. Cutting back and focusing on quality for a century or two seems like a good idea.

Trying to proselytize or raise a crisis about fertility is pointless.