DeFi exchanges, as you call them, don’t take custody of user’s funds
Can you prove it? From my experience with DeFi, the software is closed-source. You can export private keys and the like, but you can't know with certainty if another entity holds your keys as well. And in my opinion, if another entity holds my keys, it isn't self-custodial, regardless of what I do.
Mixers are getting outlawed, and it's not surprising because what they do is basically money laundering (in a sense that the procedure is literally built to hide the origins of money, both legit and not legit money). If someone is that much into privacy that doesn't care for Bitcoin's pseudonymity, then like others said, there are private coins for that.
Right, as if you don't mix your coins with other people's coins in private coins, or as if private coins aren't "literally built" to hide the origins of money (both "legit" and "not legit")!