But you miss something
More of the social problems (which I don't deny exist) are derived from illegality than from any intrinsic property of the drugs themselves.
* People don't (usually) commit crimes to fund their addictions to alcohol, tobacco or the Internet.
* People only take freebase (crack) cocaine because cocaine is so expensive. It's only expensive because it's illegal.
* People are dissuaded from seeking help at an early stage (when it's most likely to be effective) for fear of the consequences.
* Accidental overdoses from purer product than the user was expecting and poisoning from adulterated product are the results of poor quality control, but there is no incentive for good quality control.
* Electrocutions and fires in cannabis grow-houses are the result of improperly-wired electrical systems, because there is no requirement to adhere to regulations.
* Once you know you are going to be treated as a criminal just for possessing a substance, it's psychologically much easier to commit another crime. ("You may as well hang for a sheep, as for a lamb")
Most of the street price of illegal drugs is spent on working around prohibition; a night's entertainment typically costs pennies to produce, and if this was legal, even heavily taxed, there would be no profit to be made operating outside the law.
I *guarantee* you that if something you consider fairly innocuous (coffee? chips? beer? -- oh, but you already tried that one) was banned tomorrow, then before next Christmas there would be an illegal market exactly parallelling the present illegal drugs market, with equivalent attendant social problems.