Most of the business which are in money laundering are no longer using these Mixers. They have much better options to use rather using Bitcoin. They can simply buy XMR (Monero) and use that as it's a private blockchain. No transaction can be tracked. And then you can even use Monero to then get it converted into real fiat money. And yes, that's true. Mixers alone are no longer suitable for money laundering.
I had a few time debates with the mixers and their dark use case but ended up with a person who really wants to under money has the best option to use the cash, where tracking of the funds becomes near to impossible as there is no digital record. In the counter question for the few times with Bitcoin a source of money laundering I had so conversation on why Bitcoin can be a dark dream to the money lenders. In some reported cases the media used mixers money laundering was done and there was a lot of evidence as well but I did ignored them on some level.
I was totally unaware of the XMR (Monero), seems like as sir you have said there can be potential money laundering usecase why they designed their blockchain on that scale, I had heard about Stealth Addresses and Kovri features on the XMR but I did never studied them. What can be their primary purpose to design a private blokchain,with such privacy, obviously a person with white money who just need privacy wont use it as he don't need to hide his assetson that scale because his motive can be to just not get extra attention on his funds.