No. While you're right that highly sophisticated transaction and mixing protocols like Monero or (Coinjoin..)mixers cannot be traced directly it can be done in the most cases indirectly. Successful scammers have to manage earlier or later a high number of addresses. E.g. if someone is doing 500 transactions and is only once or twice co-spending the wrong coins (e.g. unmixed with mixed or monero-forth-back-exchanged coins) then the house of cards collapses often.

I was able to link for this reason more than 20% of a Wasabi mixing transaction outputs to their inputs. If you think 20% is not so much then this was the success rate per single transaction. If people are doing hundreds of transactions then only a low % of scammers are able to stay untraceable over time. The scammer ripping off 307 BTC from Exmo exchange in December moved the coins for obfuscation reasons more than 300 times before he did a mistake by co-spending it with other coins. All the 300 transactions were finally a waste of time and fees.

The scammers human brain thinks two or three steps deep but the analytics software goes much deeper. E.g. scammers which move the coins in long transaction chains use manually chosen transaction amounts. They have other patterns then natural transaction chains where A is trading with B and B is buying something for crypto from C.