Cryptocurrencies are good for nothing except ransomware, speculation, pump and dump scams, pyramid schemes, and wasting energy and advanced manufactured goods.
They are not decentralized since most people rely on dodgy online exchanges, and they are not good for international transactions because exchanges (particularly outside of the USA) charge large commissions for deposits and withdrawals.
With some of the largest financial institutions in the world having a net interest margin between 250 and 300 basis points, I cannot help but think there is some potential for decentralized finance to somehow give at least a portion of that margin back to people. It's going to take time though. When you are moving money around, you cannot break things and then ask for forgiveness later. Good engineering practices will need to be brought to the space. Good risk management will need to be brought to the space. I'm curious as to what this will all look like when things mature. Will we be able to transfer the entire functionality of a bank into a smart contract someday with all of the regulatory metrics currently attached to traditional banks fully intact?