This argument is too dismissive for me to bother spending time on it except to say this: try to think about other factors than just availability, because it's not the only thing that matters.

Here's an exercise for you to do just that. Alcohol is legal and extremely available in the west. It has an even stronger addiction potential than opioids do. And the majority of people in the west drink at varying rates. But the rate of addiction is generally under 5%(in the west). Why do you think that is?