What you're suggesting would be impossible to keep under wrap. Like you don't truly think there are a bunch of doctors out there that are just keeping this all bottled up in the modern era? Like, they figured out these super complex problems and just won't tell you because "reasons" and somehow got everyone on board with keeping the secret? None of them but brave RFK Jr and a few others that aren't doctors were willing to break ranks and tell you autism is caused by the MMR vaccine?
Sadly the world is not that colorful. Cancer is on the rise in the US and we don't know why. Autism and gender dysphoria is poorly understood along with a host of other behavioral issues because we in America really just couldn't give a fuck about things like that until recently. It kind of feels like you're reaching for a conspiracy because the reality of it is more harsh.
I don't know why you threw myocarditis and infertility in there. Those are pretty well understood.