Should I really care? When you get paid with cash do you think about the things those bills were used to pay somewhere in the past? I sure don't and I believe you also don't do it.
Well you really should, with the pandemic going on and all lol.
In all seriousness though, it shouldn't matter in most situations. Taint analysis requires a fairly sophisticated process for accurate results, and that usually means they're fine-tuned enough to detect if 'dirty' coins changed hands.
As far as I know, in some countries this is strictly prohibited, and may even fall under criminal liability.
You may want to cite a source. All mixers that have been shut down so far were not shut down
just for being a mixer.