Absolutely. BTC was quite fungible in its early days. Also you could always checkout your trade partners address. That's also when Bitcoin took off in Silkroad.
Then Bitcoin got listed on CEX and states demanded KYC which started to deanomyse the chain retroactively.
Nowadays 99% of people come into BTC via KYC (and IOUs). Which gradually increases the amount of known UTXO.
Fungibility is a hard property for money. It's either granted by law (cash) by it's material properties (gold) or mathematical enforceable (privacycoins).
KYC/AML is meant to transform money (be it Bitcoin or fiat bank accounts) into social credit, which by definition doesn't have the properties to work as neutral medium of exchange.