I think it's undisputed that there would be a lot fewer deaths per addict if the heroin available were (1) of a known concentration, (2) not fentanyl, and (3) devoid of other harmful adulterants.
The problem people argue about re: legalizing heroin is that they expect the number of addicts to rise.
Having made poor choices in the past (drugs) they now have the neuro-chemical pathways cut into their ~brians~ brains; literal ruts that signals will prefer to get to the end-state (high/low).
With enough use, heroin doesn't leave a person with choice, but rather impulse.
[edit] lol, brians [/edit]
n.b. My brother died of a heroin overdose. He made that decision himself and the existing laws did not help prevent.
FTFY. Since you care so much, please grant me control over your life to approve what you consume.
Use of pharmaceutical grade psychedelics in a clinical setting might have some benefit.