Well, it's not enough to be useful. It should be better to justify the extra energy consumption. Especially given the climate change. Also, you forget that we actually don't yet know (no one has estimated, as far as I'm aware) the realistic consumption that we'd see with wide spread adoption. And without that, it's very hard to argue and say that it's worth it because of the usefulness. Because we don't know how much we're talking about.

So I think the energy argument fails on it's own. Also, it should come at least with strong supporting arguments claiming the actual benefits. But I do agree that cryptos are worse than the currencies we have and existing block chains (I'm aware of) don't make sense even as a distributed transaction tracking system for fiat currencies.