Whether you like it or not, when you talk about a mixing service, you automatically mean it as being used to move money obtained illegally, in order to lose track of it. Therefore, even if our use is not for this purpose, this is the tag that these services have before the authorities.
The Dutch authorities disagree with you:
Yes it is true. It all depends on how it is used.
That's why I compared the current situation of mixes to torrent sites. Are they illegal? No. Can they be used? Yes. Could they contain illegal content? Yes. Does everyone use it for this purpose? No.
In the end, it all comes down to how the person will use the service and how the service is set up. And this is what can still be difficult to perceive in current mixes.