Furthermore, the decentralized nature of bitcoin cannot last indefinitely, and arguably has already ended. All mining nodes need to have a record of all balances, in order to verify that incoming transactions are valid. This places a limit on the ability to contribute to trust by mining, and will result in further centralization of miners. If a cryptocurrency were to replace fiat currency, it would not be a change from centralized currency to decentralized. Rather, it would be a from a centralized currency controlled by an elected government to a centralized currency controlled by conglomerations of miners.
I have done my best to understand their use, their applications, and their limits. With that in mind, I believe cryptocurrencies to be a obfuscated form of pyramid scheme, with additional externalities of heavy power use.
I agree it doesn't sound like the most efficient system and these incentives are somewhat perverse, but there weren't any systems like this before bitcoin. If cryptocurrencies do have valuable attributes that cannot be attained by conventional currencies and bitcoin introduced these concepts to the world in the first viable way and the popularity of these networks has lead to people researching more efficient analogues such as proof of stake and the techniques mentioned in the original article then can't we still say that the existence of bitcoin had a utilitarian benefit for the world? If the popularity of bitcoin goes down and these more efficient networks supplant it then the total energy-expenditure should be minuscule compared to the total energy usage of all humans over all time. Given the the rate at which these technologies seem to be maturing it will likely still be a lower expenditure than bootstrapping many other equally useless human endeavors.