I do not understand the mixxer issue anyway. If I wanted to anonymize and launder my money, I would use FIAT.
Unless you are a billionaire with many connections, if you tried do to that with fiat, at least in the US, you would be in jail within days.
The government does not have full control over the money laundering that is happening with fiat. I argue they have less control over fiat laundering than they do over crypto laundering.
And I am pretty sure that billionaires all have connections.