Bitcoin is not fungible, so dirty coins can easily be identified on the Blockchain.
No. Bitcoin
is fungible. There are no dirty coins, there are only people claiming they provide a service which can de-anonymize the blockchain to an extent, and which is evidently inaccurate and based on utter guesswork.
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.
The transparency of Bitcoin is not to make transactions identifiable, but to retain the property of open-source, free software.
The public now believes mixing is a very bad thing (thanks to government propaganda and misinformation).
Misinformation appears to be pretty effective based on your post.