For example would you say that smartphones are wasteful because they allow us to communicate more frequently than we could before, thus they don't strictly replace an existing consumption of energy?
That seems like a silly interpretation to me. Of course our energy demands rise as we develop and use new technologies. It's because we are doing more things with them!
Also, as I mentioned in another part of the thread, I don't think it's obvious that cryptocurrencies won't replace any existing usages of energy.