Except that one can’t necessarily track who owns an address and one cannot trace coins through a laundrette. Sure if someone’s coins are traced back to a money washing service then they could be assumed dirty but there can be other services that look like “lots of people send money to addresses. Those addresses send money to a few central addresses. Those addresses send money out to many addresses.” For example a crypto exchange. This is even harder to track if the dirty money is transferred to some other currency, sent to another exchange and then transferred again. Sure you could trace it with the cooperation of the exchange but that might not be so easy to get because exchangers don’t always live in very legally reachable countries.