off the top of my head: DeFi, NFT's, data storage, services for the bankless, decentralized metaverses, insurance, synthetics, music streaming, video streaming, social networks, DAO's, social money
I see plenty of value in many of those issues. Some appear to be just jargon or beg the question. I see zero evidence that cryptocurrency is necessary or even beneficial in solving any of those problems.
I don't think my, or any, national currency is secure forever, but neither is any cryptocurrency. Currently national currencies are, on average, far more stable and secure places to hold assets than any cryptocurrency.
If your national isn't as stable as you like, you can more easily use a different national currency. If your country has capital controls that prohibit this, then you are using cryptocurrency to break the law.
My contention is that so far the only use cases cryptocurrency has been successful in are illegal. If the legal restrictions in those areas were removed, cryptocurrency would no longer be useful there.