I'm interested in facts, not rumors.
Chainalysis says that Coinjoin introduces taint: https://go.chainalysis.com/rs/503-FAP-074/images/Advanced-Ob...
I believe that if someone uses something that's private by default, then its okay. However if someone uses someyhing that isn't private by default, but goes through efforts to try to hide the source of the funds, then it's suspicious.
Authorities follow Bitcoin transactions and ask questions which points them right to you.
This is what these investigators do all day... track money as people try to move it around. They are good at their jobs
You pay a few percents of fees, and it's not "the NSA will not be able to find you", but it was more than good enough for my mildly paranoid ass.