I think the same arguments can be said about P2P during the file sharing era. File sharing was often used for sketchy purposes most of the time, like cryptocurrencies, and people argued the underlying technology (P2P) was the key breakthrough especially for legal applications. While there are some minor cases of using P2P these days, it really hasn't made the impact that was expected. I don't see why the same won't happen for blockchain and technology underlying cryptocurrencies.