That's why you use mixers. Good mixers will completely break the chain between inputs and outputs.
Why are mixers legal? The only purpose I find on them is to money launder.
The purpose of mixer was not for money laundering and it to provide people the privacy they need which is the reason why they are legal not because hackers seized the opportunity of using it.
They are literally useless if you don't have anything to hide.
No, they are not and if you're whale you'll understand that you actually need to keep your holding from the public and not to be hackers target thats the usefulness of mixer.