The reason that crime such as robbery is associated with drug users is drugs are too expensive and the fact that gangs control the drug trade and also commit many of these violent crimes. Making things more available
should drop prices if policies are implemented well.
The US opioid crisis has been caused by a multitude of factors, including endemic poverty in some communities combined with physicians being told by producers that the compounds they were prescribing were not addictive (that was a load of shit delivered to increase profits, obviously a bad thing and we need to train physicians better on basic pharmacology). On top of that, now that restrictions have been increased on prescribing people have shifted back to the black market where nothing is regulated and you might get fentanyl hotspots in your heroin which is definitely one of the big reasons for overdoses today. Overdoses were slightly lower when pill mills were operating because people knew exactly how much of what was in the pills they get from Walgreen's or whatever.
The issues I'm referring to are the ones that have been present for much longer. These issues include things such as lack of employment due to drug users having a record, discrimination against users in general stemming from the stigma and association with violent crime (even though 90%+ of users are nonviolent), stigma in treating addiction and mental illnesses, overdoses which almost always stem from a change in how the in regular d suppliers cut their products and change potency (people get used to a certain concentration of active and if that changes they may easily use too much), and the lack of drug education due to the "just say no" ideology which essentially lied to multiple generations about the dangers and mechanisms of psychoactive compounds.
When it comes to alcohol, there are socially learned ways of managing use of the drug (ethanol) in a responsible fashion. Only some small communities have learned how to use other drugs responsibly due to the stigma preventing spread of information.
We also don't have a lot of information on the intersection of these psychoactive compounds and mental illness. Its possible that there are people who have malfunction regulation of endogenous opioids (endorphins) or their receptors which a partial agonist could be used for therapy. There is literally not a single doctor who would prescribe an opiate agonist for mental health issues because the research on things like that is all but banned due to the DEA dragging their feet and refusing to give people licensing to study the compounds (MAPS has had to sue the DEA over this issue). Combine this with funding issues, where only studies looking at downsides of psychoactive get funded and now we have an extremely skewed/biased view.
There are even more issues than I've presented here, but these are the ones at the forefront of my mind when I consider the issues of drug use today. Almost all of these issues have their root in the prohibition of these substances. It would be far easier to not only study and understand drugs without prohibition, but people would also overdose less due to having a reliable, regulated, and affordable supply. The primary issue that feeds into this which isn't due to prohibition itself is poverty, and that's a whole 'nother thing.