Can we just put aside the other worries and address the main problem? I want to believe Sending bitcoin (either Utxo that has been KYC or not) to a mixer is risky because even if you know a little about their protocols,  you don't have the associated private keys to your deposit and you risk losing your money but no one is discussing that which I'm having interest on.
If not for the fact that some Mixers claimed that they usually purge their logs, why trust a mixer that can be threatened just like an exchange? why not go through Coinjoin where you have access to your keys than a mixer that you have to trust about your privacy and custody of funds.

@o_e_l_e_o