The problem is always in the services of the third party, and these can be controlled by the government easily, for example you need the service of the third party in order to trade Bitcoin which is exchanges, of course the government can control the exchanges in that country and force them to request verification through KYC In such a case, the government will be able to view all transactions made by any person who trades in this exchange and pursues it.
This is what governments are doing now and we see an increase in exchanges that are requesting verification by KYC.