> It is far from trivial. What are you going to do if the money goes to an enemy country?

Who send it?

> And while cryptocurrency are certainly popular with criminals, it is far from the only option for hiding transactions.

Start by removing the cryptocurrency option, that's an easy win. Go after other options afterwards. Removing cryptocurrencies is not going to stop all the crime but it will stop a lot of it and push criminals to more risky and easy to trace ways of getting money.

> how to you expect them to stop well organized international gangs, sometimes backed by nation states.

Removing their financing like cryptocurrencies. All that you say is that crime is impossible to stop. Bollocks. Start by banning Bitcoin and other crypto-crime-enablers and continue from there.

You gave zero arguments to why cryptocurrencies should not be banned.