From the perspective of preventing people from using drugs, it is a failure, but it is clear that was never the goal from the start. It is successful in systemically and extra-judiciously oppressing a lot of peoples, often to the benefit of the prison-industrial complex. The war on drugs has also benefitted the military-industrial complex and helped to quell leftist insurgencies in foreign countries, like Colombia.

Wars against vague notions, like drugs or terror, let the government pinpoint its enemies and deal with them how they see fit.