You're wrong because bitcoin's fungible that's the way Satoshi created it. Bitcoin's got nothing to do with identifying dirty or tainted coins on the blockchain. Bitcoin was created as fungible that can't be denied but if we're talking about govts wanting to control crypto by regulating it's a separate point.
Bitcoin is not fungible, so dirty coins can easily be identified on the Blockchain. The transparency of BTC is not a bug but a feature. It's a great way keep an eye of the flow of transactions on the network. This can help detect malicious actors on-chain. Addresses don't have an ID linked to them, so there's no way to tell the coins belong to you unless governments use surveillance/analytics tools. Using a new address for each transaction, avoiding centralized exchanges, and using a mixer would be your best best to help protect your privacy.