The most significant disadvantage of Crypto is that it is easy to be used by criminals to commit illegal transactions and this is also a big reason for the government to ban it. Also, the issuance of Tokens is too easy to create fake projects aimed at appropriating investment funds of investors.
It has become an unsolved problem until now but Bitcoin is a freedom so everyone can commit crimes with Bitcoin transaction tools.
Not as unsolved as it seems. For instance, US intelligence agencies nowadays manage to track down many fraudsters committing crimes using Bitcoin & Ethereum. AFAIK it's still really hard for anyone to track anonymous systems such as Monero & ZCash.
Considering Bitcoin, many blockchain analysis tools already exist, e.g. Chainalysis, Coinfirm and others. There are far more ways to track down Bitcoin transactions as it seems at the first glance.