Lots of people believe essential oils can cure cancer. Any big oncology center has stories about people who show up presenting horrible symptoms well beyond what's normally seen. They spent 2 years just doing essential oils or whatever (often encouraged by some a quack) on some readily treatable thing and when they do finally give in and come to the ER it's basically too late.

Tragedies like these make me very hesitant about "harmless" falsehoods.

I also wonder what cancer survival rates look like if you filter people who self select out of conventional healthcare for a period of time like your example above.

I wonder if belief in alternate medicine correlates with unaffordable healthcare. It is much easier to believe that there is a better way if the correct procedure would ruin you financially.