Harm reduction is a series of publicly funded social and rehabilitation/substitution programs that has absolutely nothing to do with legalizing any sort of drugs. Legalization is an entire different question, just don't try to make "harm reduction" yet another buzzword for legalization.
Currently junkies need the dealers to get their supplies. So they have to support crime, to meet their needs. And they get bad quality with usually extra poisenous additives. Legalizing would immmediately reduce or remove those 2 harms.
But I agree that we should not stop there, but rather help them stop being junkies at all, with various help programms. I just happen to think it is easier to reach people in legal ways, than criminalize them. But you seem to disagree here?
Harm from drugs in the current system goes well beyond the individual user.