I guess if you want drug use to go down, or to reduce deaths etc. if those specific metrics are you goals, and nothing else matters, that's one thing. Maybe it is not "working" by those standards.
But I don't want a government having any opinion on what people put into their own bodies. It is a health/medical issue and, in a broader context, a liberty issue. It is not a legal issue in my opinion. Regardless of drug use statistics, no one belongs in jail or with a criminal record for no reason other than possessing and/or consuming an intoxicant. I don't even care if drug use goes up with decrminalization or legalization. In my opinion it is simply outside of the proper moral scope of a government to concern itself with such matters. Feel free to disagree. This is my personal political view.