Maybe in the U.S., less so in China where ~25% of adult males were opium addicts in the early 1900s. The war on drugs isn't a success by any means, but at least the problems that exist aren't on that scale.
A better example of prohibition backfiring is with marijuana, where before prohibition ~0% of Americans were marijuana users, whereas today ~85% of American adults have used marijuana.
The number of people who use opioids regularly is a second-order concern (if only because fent-laced heroin certainly gets that number down) to me, frankly -- reducing morbidity and mortality due to drug use is a lot more important. With a decent medical infrastructure, addicts should be able to get opioid maintenance therapy with the right drugs and dosage and be able to lead actual interesting lives beyond trying to score the next hit.
I'd so much rather live in a country where people who want to get high on opioids can buy cheap, pure, precisely metered opioids that won't kill them rather than smashing car windows to be able to pay for overpriced fentanyl-laced drugs sold by criminals that might overdose them in the street (which will cause even more expense and load on the already-awful USian medical system).
By comparing the anecdotal regular users in the 1930s to the current population that has had at least one use you are purposefully making a faulty comparison. Why did you not compare past and current users?