To remain anonymous is only possible if people will not convert Bitcoin to Fiat.
Exactly thats right on point. When you bring in fiat currencies you will need to comply with its issuing government's laws. In the purest form, BTC is meant to be obtained by mining and used as currency among the people, exchanges changed it all when you could "buy/sell" BTC with fiat currency.
But as of recently, it is hard to purchase any crypto without encountering a form of KYC.
There are still ways to avoid KYC while using fiat by doing OTC P2P trades, there are also DEX such as Bisq where you can do P2P trades online which the need of KYC like it was the case with localbitcoins back in the day.