It is not merely the case that, faced with something potentially addictive, you just recall "Just Say No" and bada-bing, no addiction happens. Humans aren't robots. Humans get addicted to drugs and other activities, not just in social situations but also as a coping mechanism for life failures they can't fix, or see no way to fix. It can take years of psychological work to break the cycle of dependence, and in some cases it might not even be possible.
If you have time for a moving speech, listen to Craig Ferguson's monologue on his own alcohol addiction, his path to sobriety, and the constant vigilance needed to maintain it, which he gave rather than joke about Britney Spears' public freakout in 2007: https://www.youtube.com/watch?v=K46P7loICXY
I know there are such people, but they are a small minority. If "addiction" is only talking about them, then the response to the GP is simple: sure, "Just Say No" doesn't work for that small minority, but it can still work for everyone else, and shouldn't be discarded on that account.
My read of the GP is that they were not using "addiction" in this narrow sense, and my response was based on that interpretation. But they're welcome to correct me if I'm wrong about that interpretation.
One recent example of this was the lack of free hospital beds at the height of COVID. In a pandemic, the overoptimization of nixing bed/supply reserves left no slack, leaving hospitals unfit to address the emergency.