The infertility crisis is certainly not due to sperm quality as the title suggests.
Postponing pregnancy to later age on female side seems more like the culprit.
But I guess it is modern to blame everything on men these days, so current culture will like the sperm quality hypothesis more.
It is specifically about male infertility, based on an objective measure of fertility (sperm count), which has indeed dropped over the past few decades - no one is trying to "blame everything on men".
"You need only one man with healthy sperm and 1000 women to repopulate the world."
While true, our societies are based on long-term pairs having children, not a set of elite sperm knights who go around and impregnate wives of everybody.
Both effects can happen at the same time. Yes, female fertility goes down with age. But male reproductive health isn't what it used to be either, and provably so. Taken together, those effects cause a significant problem.
We must care more about phthalates and other hormone mimicking stuff in our food chain. Humans aren't even the only species that has the same problems.
Seems like a surefire way to end up with genetic bottlenecks galore.