You are advocating a false measure of whether or not the war is "working."
If you track the rate of Opium shipments to China during the 1800s you will note that it starts out small, and then builds massively after a few decades.
This is the NORMAL progression for drug addiction in a society which tolerates it. By 1900, Drug addiction in the Provence of Manchuria had hit 50% of adult males. As a result, China wen through government collapse, Invasion, and the dictatorship of Mao. All of this stuff traceable to the destruction caused to their society by legal drugs.
Now as to your false measure of success, that notion that the ability to buy drugs = failure. In 1900, the addiction rate to drugs such as opium and cocaine was ~ 2% of the population. After 100 years of the "War on Drugs" the addiction rate is still 2%. It hasn't risen. The NORMAL CONDITION is that it would rise until it was killing a huge chunk of our population, but it hasn't. The reason it hasn't is because the war on drugs has kept it in check. The small 2% of the black market which exists is no measure of failure, it is a measure of great success given the restrictions utilized in fighting the war on drugs.
We as a nation tolerate this 2% because we would not tolerate the necessary tactics needed to eliminate it. If we actually fought the war on drugs like it was a WAR, i.e. swiftly killing drug dealers, then we could possibly do something about that remaining 2% market, but most people would rather live with it than go that far.
I will point out that Chairman Mao did solve China's opium problem. He utterly eliminated it after World War II by killing anyone caught with opium. It CAN be done, but I think i'd rather put up with some small percentage of addicts in our population.