Some cryptocurrency can be truly anonymous using some pretty interesting maths to verify things have properties without revealing the thing (in particular, XMR/Monero is the most well known one for doing this).

However, it's still crypto so it's kinda like instant distrust and heavy skepticism (though I'm slightly less negative than I used to be for the truly anonymous ones as I'm trans and while right now I can still get HRT through normal channels after being on DIY for a bit, a backroute via DIY is always something I like to keep tabs on and within current economic structures crypto of this kind can theoretically be useful as long as it is somewhat inflationary to reduce it's use as an investment vehicle, though I also am anti-currency in terms of my desired economic system ;3)

With things like BTC/Bitcoin or others with a public ledger, you can pay someone a lot to essentially mix your currency with several other people before sending it to new accounts to reduce traceability, but turning it to fiat currency is still often pretty traceable for the reasons you said. To me it also seems money-laundering-ish lol ^.^, there's definitely tons of sketchy shit involved. But it's crypto so that's par for the course ;p