Hello, I live in Venezuela and there are laws that criminalize crimes without a victim. But even though Venezuelans pass from the laws and fail them, this is increasing thanks to authorities who take advantage of people by charging money not to get them prey. (If there is corruption at all levels).
I have no answers to your questions, but like you I have doubts about it that have formed me own ideas of how to "overcome" the problem.

1. • First legalize drug use: The state must be the one that provides them by selling it on the street, drugs made in specialized, safe and pure laboratories. Sold even by the police, have a control of consumers to proportional fair amount, etc. It reduces crime and creates income for the country.
2. • Statising games of chance and betting: Being the state involved can allocate in time help the addicted people, protect the bettor who is about to lose everything, etc. The state will also have extra income and a happy village.
3. • Establish methods of aid in prostitution by the State: Prostitution is an election, we know. But these choices are sometimes taken by the pressure of the environment, a poor family, an abandoned woman, etc. as well as a choice for taste. The State should protect them by offering medical care, birth control, etc. Apply laws that protect both the client and the prostitute. Because that world sometimes lacks laws.

Well, those are my three ideas, radicals? I do not know, what I know is that it seems to me right.

Greetings.