Drinking is permissible and prohibition did not stop it. You’re not going to stop people taking drugs prohibition either. You’re best chance is harm reduction, to teach people the limits of how much to use.
We’ve already tried prohibition and at least two Presidents became rich because of it.
You claimed regulating alcohol ensured safety. It does no such thing. It will do no such thing with marijuana either.
There was indeed less alcohol use during prohibition. And dry counties have less DUIs, alcohol related crime, etc. That is a fact.
And while there can be such a thing as light drinking, there is no such thing as “light cocaining” or the like. There is no such thing as a safe amount of crack smoking.