But if you use a coin switching service that doesn't require KYC and you switch into Monero and from the provided address send it to another Monero address, it's over. There is no single way in the world to trace down transactions on the Monero blockchain, at least not from what we know to date.
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.