The war on drugs had tried and failed for decades. All it's done is enrich the cartels, fill prisons with minorities, create an oxycodone epidemic, flood the streets with cheap and deadly fentanyl, and countless other problems.
While the same government "protecting" citizens from harm is corrupt the point of the CIA becomeing drug traffickers on the side [1], making the problem even worse like throwing petrol on a fire.
[1] https://www.ojp.gov/ncjrs/virtual-library/abstracts/big-whit...
Prohibition has nothing to do with prevention.
Has it succeeded? No.
Criminalizing it often makes it even more difficult to deal with the societal damage of addiction. Dealing with an addict is difficult, but dealing with an addict who is now a criminal is that much harder.
Society has all sorts of tools to help people who are struggling. Our criminal justice system is one of the least effective.
An addict is harming their family whether drugs are legal or not, and it's obvious from our current situation that their legal status doesn't prevent people from using drugs.
An addict who is now a criminal can be forced into treatment at least. An addict who can freely buy their drugs (because we aren't prosecuting dealers either) and do them on the street anywhere will just die faster (especially with fentanyl).
I also don't see why it has to be all one way or the other. I agree that people with dependent children have no business taking risks with drugs. like you say, this creates a mess other people are compelled to clean up.
but what if a person doesn't have children (or successfully raised them to be independent adults)? as long as they pay whatever taxes they owe, why care what they do with their time?
On the other hand, what to do if some people don't act responsibly and get addicted; and then for instance ruin their health or neglect their children. Who should be responsible for helping them go to rehab, fixing their health problems or helping their children? If it means the society has to take care of this, then isn't it also fair that society tries to prevent people from getting addicted in the first place? And prohibiting drugs is one way of trying to do that.