For instance alcohol addiction is extremely destructive at pathological levels, and we have a flurry of studies coming to a "no safe dose" conclusion. But we also have plenty of evidence on what happens when outright banning alcohol at large scale and it's not great either.
I'm not sure we have a good model or understanding yet of what it actually means to have addictive substances around and their social effects.
I don't think that's true. We have thousands of years of experience. Not everything needs the perfect study taken in the perfect lab conditions for folks to make conclusions which are useful for operating in the real world.
For instance alcohol addiction is extremely destructive at pathological levels, and we have a flurry of studies coming to a "no safe dose" conclusion. But we also have plenty of evidence on what happens when outright banning alcohol at large scale and it's not great either.
I'm not sure we have a good model or understanding yet of what it actually means to have addictive substances around and their social effects.