As bad as drugs are, you can only help people that will help themselves. The cure is obviously worse and far more expensive than the disease. All you can really do is limit employment and government benefits on drug use. Prison is not a deterrent.
Voluntary commitment is the only option.
I’ve seen drug addiction up close and personal, believe me. I strongly believe that deliberately making oneself more stupid than you already are intentionally is a very poor long-term survival strategy. And you’re completely correct.
Make these people suffer for their folly as early and as harshly as possible but not one nickel of support for them. Legalize the crap and sell it in 5 pound sacks at Safeway at market prices, just like booze. If they can pay for it, fine. Smoke, snort, inject, or suppository yourself to Kingdom come. But if you OD or get sick, you die in the street. The only concession “society” makes is tossing your corpse into a standard garbage truck for a trip to the landfill.
In about a year all of the idiots would be dead and the rest of us could go on with our lives.