OK, I hope my question doesn’t get misunderstood, I can see how that could happen.
Just a product of overthinking.
Idea is that we can live fairly easily even with some diseases/disorders which could be-life threatening. Many of these are hereditary.
Since modern medicine increases our survival capabilities, the “weaker” individuals can also survive and have offsprings that could potentially inherit these weaknesses, and as this continues it could perhaps leave nearly all people suffering from such conditions further into future.
Does that sound like a realistic scenario? (Assuming we don’t destroy ourselves along with the environment first…)
Actually education is probably the largest selection factor. Educated people have less children than less educated people. Sometimes massively so. This is not necessarily linked with intelligence, it correlates more with socio economic factors.
The problem is that people don’t seem to realize the difference between causes of deaths and population declination. Even if for some reason humans everywhere agree on The Purge like laws except for every day, that wouldn’t represent a risk for humanity (as long as governments still withhold their nuclear arsenal), some cities might be all but wiped out, but the chances are humans will survive. Anarchy was the status quo for the vast majority of human existence, and we’re still here.
However other seemingly innocuous things are much worse for humanity as a whole, e.g. electing politicians who disregard climate change or that intend on using military power to take others territories can have much larger consequences on humanity as a whole. Your example is also great, because it’s counter intuitive that higher education leads to population declination, that being said I believe that also wouldn’t become an extinction event, surely the world would become a place where highly educated people want to have children before that.