Point taken. One could always go back to the "original" white willow bark that Bayer methylized into aspirin, though there are alternatives available these days.
I think the only way heroin could be considered a "good medicine" would be as a palliative in hospice care, certainly not as the cough suppressant it was invented to be. FWIW, I say that as a caregiver for someone, with MS and degenerative back issues, who has been in pain management for over a decade now.
That is true, however what is also true is that abusing them also causes problems. Tylenol for example will damage the liver, I believe it is, if you abuse it. Really even natural remedies done to excess are probably harmful in some manner. The key is abuse, as it is the real culprit.