I think your title says a lot about how you approached criticizing cryptocurrencies. The first thing I would ask you is do you think Bitcoin is novel? Do you think it was worth trying? The blockchain has applications. It will be used in the real world. I don't think a cryptocurrency will be replacing FIAT anytime, which is the marker of success you seem to have set. It already serves purpose for people without access to banking or those who wish to send money internationally. This is not something that will be even close to perfect out the gate, that is your erroneous assumption.