Honestly, "only useful for crime" is the only part of blockchain that I like. What I don't like is the energy use of PoW, the centralization tendencies of PoS, and the general unusability of any existing coins as either a medium of exchange or a store of value. I'd love an anonymous digital cash that didn't boil the oceans, enrich oligarchs, or encourage speculation. It's just that blockchain cryptocurrencies are not that.