But drugs like fentanyl and meth are still available to the general public despite being illegal. So the question instead is do the practical effects of illegality help society, and that's not at all clear.
I think if you look at areas that try to restrict the supply of these dangerous drug options you will find that that they are less available and expensive. When you look at areas like Portland/West Coast of US, you see that with increasing availability there are lots of associated problems. Perhaps there needs to be institutionally provided drug alternatives for those who have already become addicted, but id argue its very clear that lowering barriers to use has clear negative impacts.
I'm not sure that's the case. Meth and heroin was plenty cheap and plenty available in the deep south, and it's not like they're known for being soft on drug crimes down there.
I'm mean, I'm from the deep south. They have a much larger issue with hard drugs than the west coast does. The drugs are just as available despite the increased enforcement.
It takes time to see results. For instance it took a few years after Portugal decriminalized all drugs before their program really hit it's stride. There's a lot of societal infrastructure that needs to be dismantled and reconstructed for the new system and that takes time.