It's possible the BTC you have at the moment has traces of cocaine on it.. but it doesn't matter to the network.
also no one knows if the address belongs to you or a drug dealer and in the case that the drug dealer got caught and analytic's was ran on their addresses, they would hit a brick wall once they got to the transaction that went to the mixer and then another wall trying to work out who owns your address.
but you are right, there are many was to accomplish the same thing, you could use an altcoin like you suggested Monero or Dash; you could use confidential transaction or stealth address with BTC and many other means;
i use this mixed to transfer coins between trading accounts so that exchanges cannot collude and link my accounts together; not that i am kyc'd on any of them just and extra measure i like to use.