There are fully anonymous cryptocurrencies. Also, in a public ledger, an address is not directly associated to a person.

Not immediately, no, but there's no forward secrecy, so unless users take extensive steps to obfuscate their activities, as soon as they make one transaction with a counterparty who knows who they are (such as an exchange with KYC) they are at risk of de-anonymisation.

There are also Layer 2 technologies