If anyone decides to get legal that won't wash. They are handling the money of others and moving it elsewhere with a polish of untraceability. Because of that they should be vetting the source of the money and vetting the people who sent and received it. It's just about the perfect definition of a money laundering operation. I think centralised options are on borrowed time unless they bury themselves deeply.
I wouldn't call that a
money laundering operation, but rather an unlicensed money transmitter. The latter is fairly common and carries much smaller penalties and less stigma.
Platforms that only use cryptocurrencies (no banks) are in an interesting position. The US government's attempt to take down BTC-e in 2017 highlights the fact that
properly secured cryptocurrency can't be seized. Even if the authorities seize clearnet domains and servers, companies with zero exposure to custodial fiat liabilities can just spin up new domains and servers and secure new wallets. While exchanges would suffer branding issues from such a seizure, a mixer would probably be celebrated.
With a properly run mixer, the most that US or EU authorities can do is seize the domain. That's rather embarrassing for them. The public optics around playing cat-and-mouse games with mixers and clearnet domains aren't worth it. That's why we'll see low hanging fruit like Helix -- operated from the US -- taken down, but not others.