I came across a news item in Canada saying Heroin is basically impossible to find now. The lower quality but much cheaper product has replaced it. Clayton Christensen's theory of disruption in action.

There’s a graph in this very article that answers that question. Heroin deaths have declined significantly as fentanyl has displaced heroin on the market, but fentanyl deaths are far higher than heroin deaths ever were, because it’s far easier to OD on.