I don't think cryptocurrencies are protecting anyone from any problem.

OK, I'll bite. How is Monero not protecting people's privacy?

Because most Monero transactions are traceable, according to research by the National University of Singapore:

https://eprint.iacr.org/2017/338.pdf

If anyone can debunk this I’d love to hear more, but generally I think it’s dangerous to rely on claims of secrecy

Thanks for the link. While it’s good to see the paper overstates the problem, it’s also clear that users should not assume that their Monero transactions are untraceable.

I think the summary of both papers (the initial paper and monero's unofficial response) could be that monero's transactions are reasonably untraceable.

Reasonably private should be good enough for most people.

If the goal is more-private-than-bitcoin, yes, it's less traceable than bitcoin. If the goal is bulletproof-from-authorities, not so much.

Yes, a known example is Monero. The question is, first and foremost, if you should trust cryptocurrencies.

You don't, that's the point. It's an investment of time and money to learn the tech so you don't need to trust it.

Trustlessness, in other words the property of not requiring trust in the ledger's correctness, is the cornerstone of cryptocurrencies.

Yeah, but the biggest ones are not inflationary, so they end up as exclusively hype-driven speculative investment vehicles. That's not good for a method of payment.

Monero is inflationary, but it still might not keep up with coin loss.

Even a coin with higher inflation will still be susceptible as a speculative-investment. It would be nice if there was a way to avoid that, and to keep value relatively-stable, but I can't think of anyway that does require trusting 3rd parties.

Typo, meant: "that does not require"

Preserving privacy by having a public ledger where everyone can see your transactions?