However it is less harmful than most organic options overall. It is completely harmless to humans or other wildlife. It doesn't build up over time.
You are right that a so-called natural pesticide like rotenone seems to be even worse. They were able to induce parkinson with it in rats in just a few weeks. But also Glyphosate is looked at with a lot of suspicion.
Take this case study, they refer to several cases and epidemiologic research: https://pubmed.ncbi.nlm.nih.gov/30799335/
Considering the medical attention and research it gets, I see no reason to be as sure as you are. Especially your believe that "it's completely harmless" seems to have no solid reasoning behind it.