The legal side of it is just that; one side. It's important, yes, but just legalising opium won't automagically solve the opioid crisis on its own. We also need to address societal causes of opioid addiction. At least in the US, overprescription from doctors corrupted by big pharma(especially purdue), is one major contributing factor that's been thoroughly exposed in recent years. Obviously the role of money in medicine needs to be changed.
The deeper issue though is that more people are becoming vulnerable to developing addiction. Speaking as an addict myself, one of the root causes of addiction at an individual level can be untreated mentall illness. Drugs can often provide a temporary reprieve from mental illness, and unfortunately is often more easily available than good treatment options. In many western countries, funding for mental health treatment programs has been reduced. This is contributing to a rise in unmanaged mental health issues.
I think spending a ton more on mental health, especially in youth, is essential to reducing the prevalence of addiction.
Other issues include poverty, unemployment, housing. The thread through all of this is that more people lead miserable lives, and that makes drugs more tempting.
But let me circle back to the legalisation issue and why it's so important. The main health risks with opioids are overdose in the short term, infections(hepatitis, HIV, endocarditis) from dirty needles and organ damage from dirty drugs in the longer term. Legalisation can address all of these things. Any addict will tell you the main reason overdoses are so common is there's no consistency to the potency of their drugs. Even when it was still heroin, the constant battle with LE meant the purity would fluctuate wildly. Add to that synergistic adulterants, and now these hyperpotent drugs, and you get addicts dying like flies. Legalising the drugs would allow regulating them and providing consistent dosages, eliminating harmful adulterants, and mandating that doses be sold alongside clean user equipment. This would greatly limit the health impact of these drugs on its users. It's obvious that recovering from addiction would be a lot easier if your body hadn't been destroyed by it before you even enter a treatment programme.
In addition, remember what I said about funding for mental health declining? How much money is spent futilely fighting the war on drugs? I haven't done the tedious task of adding up federal, state and police budgets for the US, but the budget for the DEA alone is in the billions, so it's safe to assume once you do the math it'll be in the tens of billions for LE alone. And that's without accounting for the courts, prisons, and all the money being funneled away from the legitimate economy by criminal gangs. This is money that should be spent elsewhere. On mental health and addiction treatment, housing, social programmes. But instead it's essentially being piled up and lit on fire.
So at least for me, that's why I keep saying "let them take drugs".