Even if the War on Drugs was cancelled today, we'd still be dealing with the criminal effects for decades. When prohibition was repealed, all the criminals who had been bootlegging didn't decide to start living straight lives, they switched to other criminal enterprises. Prohibition was a big part of how the mafia got a foothold in the US.

Its even plausible that massive decriminalization would lead to more work for the police. I'd like to think it would be more productive work though, instead of just hassling easy targets like so many do now.