I think there's differences - boycotts are groups of individuals refusing to buy from corporations, whereas cancel culture often targets regular people, any may even be instigated by powerful institutions. Boycotts are far more morally acceptable than cancel culture IMO.

Even if boycotts and cancel culture are identical, I don't see any further point in denying that cancel culture works. People have been saying that cancel culture is bad for years now, and that hasn't stopped the cancellers one bit. Refusing to participate in it due to a false sense of moral superiority is foolish.