On the extreme scenario that there is zero privacy, then their software source code is neither private, so we can all see how their accuracy function works, which is the first step to devaluing it.
The fact that Chainalysis are fighting so hard in court, using every means available to them, to prevent
anyone from even looking at their source code should tell you all you need to know about how accurate it is (i.e. completely made up bullshit). They know if their code is exposed and everyone sees first hand what a scam it is, then their profits tank.
I'm strongly of the belief that majority of the Bitcoin in circulation is used in legal transactions.
If you (not you personally) are going to buy in to the bullshit that blockchain analysis companies peddle and accept their made up analyses, then you also have to accept their figures which show that the amount of bitcoin being used for illicit purposes is miniscule, and a far lower percentage than the amount of fiat being used for illicit purposes.