That's not a reason to ban it. The issues are caused by the user, to the user. If users are causing issues to others (violence, theft, drunk driving, et c), those are separate and already-illegal things that can and should be enforced. Arresting people for possession is basically like arresting them for pre-crime: "some other people who possessed similar things later went on to commit actual crimes, so you go to jail out of fear" is not a sane approach.
The possession and use of substances for the human body is plainly the wrong place to legislate: the war on drugs in the US has been a costly, racist, unmitigated disaster.
Yeah, except when those hard lines intersect the bodies of others. Nobody has the right to tell me what can or can't go in my body: that's exclusively my decision.
For alcohol? I dare you to say that to the face of someone with alcohol addiction in family. It's a simplistic black and white view. We negotiated thresholds where alcohol is restricted (age, distribution, setting) while not banning it completely. Neither unrestricted access nor prohibition were the answer.
Whatever you think is working (stopping sales at 2am or whatever) isn't. It's farce. Humans can't handle drugs, generally speaking, and permitting some whole ruining lives over others is the peak of ineffective ridiculousness.
The fact that humans can't generally handle drugs (alcohol included) is not a reason to waste time and money and imprison millions of people in a misguided attempt to address the problem. (Not that that was what the war on drugs was even for, mind you.)
The issue is that we expect most people to have a drink once in a whole and continue with their lives as usual. We can't realistically expect recreational heroin use with no long term issues.