For some additional important information that you should know, fiat is the most used currency in everything, you name it, and that includes crimes and other illegal activities even it's already being regulated by the Government. You see, the blame shouldn't be in cryptocurrency or fiat, it is us who made the choice, on where we are going to use our possessions.
Cryptocurrencies being use in illegal things will not affect the market, and the system that you were saying has nothing to do with it, blockchain is completely perfect that is why criminals preferred to use it than fiat.
You mean the anonymous being of crypto has taken advantage by these criminals? Actually this isn't a good excuse for them, because the exploitation of the system was generally driven towards crypto, which the one involved with this cannot be traced directly. Maybe there's somebody whose ignoring this issues arising. Illegal activities related to crypto needs to be eliminated, to lessen the occurrence and government should take action on this concerns.