By doing "nothing", we gain other things such as financial privacy for everyone and making digital payments available for everyone. These are not insignificant things and if they're more valuable than the inefficient anti-laundering attempts then doing "nothing" would indeed be better.

Also we wouldn't truly be doing "nothing", we would only give up one traceability component and we can still chase crime in other ways, like requiring documents of where you got the money to buy this mansion.