The major difference is that opioids had been used for pain treatment in modern medicine decades before the war on drugs, so legal prohibitions on recreational

The major difference is that opioids had been used for pain treatment in modern medicine decades before the war on drugs, so legal prohibitions on recreational opioids didn’t affect basic research nor the development of new treatments, nor did it affect the legitimacy of opioid treatments in the eyes of the US medical establishment. (perhaps it should have!) By contrast, psychedelics have not been used in medicine and were/are not considered “legitimate” by the medical establishment. So with legal prohibitions on actually obtaining and administering psychedelics, the War on Drugs actually did hinder psychedelics medical research.