There is an endless discussion that involes freedom of speech and freedom of privacy. Mixers are good but can be used by criminals and North Korean hackers. Is "bad people use it" enough to prevent actual privacy seekers? I for one would like for mixers to continue to exist, and in a utopian way, only be used by good people.
Maybe @FIODNederland can comment on it.

A complete discussion of the legality of mixers is like a perpetual mobile. If mixers were to check assets before mixing, then they would lose their status as an anonymization service. Again, if they allow all transactions, this automatically marks them as a money laundering service.
In fact, the whole process was failed by those who are supposed to prevent the theft of money, corruption, illegal trade and whatever.