The Short Version
The claim is largely accurate. Multiple peer-reviewed studies, WHO data, and medical authority declarations confirm that unproven and pseudoscientific health practices are widespread — with documented harms including hundreds of thousands of preventable deaths from HIV denialism and billions in excess healthcare costs from vaccine hesitancy. However, the claim slightly overstates the case: commonly cited prevalence figures measure broad complementary/alternative medicine use, which includes some evidence-supported practices, not exclusively pseudoscientific treatments.