I will never make this, because this would make my BTC suspect. And there is a risk to make my BTC's dirty.
When you talk about tainted BTC, then you should know that you also very likely have BTC that originates from some problematic/suspicious transaction - so if someone really wants to analyze the history of your BTC, a link to some dirty coins would not be strange. All those who would be strictly guided by accepting only
virgin BTC would very quickly find themselves in a big problem.
Of course if we make the change on a CEX, it would be possible to trace back the origin, because the CEX will have a history-protocol. But I guess not, when we make this via DEX.
I know that Bisq works in such a way that each user has the software on his computer, and the connection between users is via the TOR network, so that the user's privacy is ensured. I cited it as an example of DEX, which is often mentioned in a positive sense when it comes to secure and no KYC trading.
If I am right: Why do people use BTC mixer? Isn't changing BTC into another crypto and change them back, not the much better solution to cut off the trace?
Not all mixers are the same, and even the best ones cannot ensure user privacy if they use them in the wrong way. The goal is not only to break the link between your deposit and what you will get as a result of the mix, but also to be smart and use mixed coins with a time delay to make it difficult for someone to connect deposit A with withdrawal B.