That is true.

On the other hand, while I'm (unfortunately for this discussion) not an expert in money laundering laws, the police tend to confiscate money that is known to have been laundered (or even before they know for sure apparently). Since Bitcoins are trackable, tumbled bitcoins should be "confiscated" (by marking them as illegal for use in @countries in some kind of database) and then, if the previous owner proves that they weren't doing anything illegal, unmarked. Once there is proof of illegal activity, the previous owner could be forced to return them to the rightful owner (if a rightful owner exists, such as in the case of ransomware), or either kept marked as confiscated or even marked as permanently invalid.

Best of luck enforcing that. Just like cash, most people are not going to care if someone pays them with laundered BTC, and will ignore the law. Even if they do manage to get enforcement in place years down the road, that kind of activity will not happen with BTC. People who value privacy in their transactions already use Monero, which is superior to BTC in that respect

Quantum issue is not with hashing but with private key derivation

Oh I didn't know that! Thanks for pointing it out.

But quantum computer can break currently used Public-Key Algorithms, like ECDSA, which is used by Bitcoin.