To be fair people are not overdosing because they are taking Fentanyl they are overdosing because they don't know how much Fentanyl they are taking or that they are taking it at all. Imagine if every time you drank a beer you didn't know if it was 5% ABV or 95% ABV spiked with moonshine how many people would be dead? That is why alcohol is regulated and even drunks rarely overdose and die. When you regulate drugs and people know what they are getting and the dosage overdoses and deaths fall to near 0 levels. The war on drugs is not about saving lives.
https://www.washingtonpost.com/news/wonk/wp/2015/06/05/why-hardly-anyone-dies-from-a-drug-overdose-in-portugal/
Here in Portugal people are so poor they can't afford high doses. Never heard of meth or fentanyl over here.
Regarding the "decriminalize" use of drugs i read all the time in foreign publications,, it's not that linear. If you are smoking pot in public you get arrested. Not prossecuted, but arrested. You get a slap on the wrist by the judge. If you get many, you will face jail.
Hell, if i get caught with a few ampouls of roids, i can get charged with trafficking. 6 years.
The "portuguese example" i read all the time, is something that doesn't happen here in Portugal, only in Joe Rogan podcasts.