It is inevitable that most if not all mixers will be used for (or will be attempted to be used by criminals for) nefarious purposes
Then why did you join the signature campaign of one of the mixers? No offence, I am just asking because I think you shouldn't join what you think are used by criminals.
"Elliptic" is a crypto tracing company and they have suggested there is irrefutable evidence $22 million moved from Blender to Sinbad in the very early days after Sinbad was created therefore that doubles the reasons why it will probably be the next mixer to be shut down sooner rather than later.
But that does not mean that good people are not using mixers too.