I don’t encourage using centralized exchanges to buy/sell bitcoins for people who care about privacy because you have to do KYC. It’s better to use decentralized exchanges like bisq to trade your bitcoins to fiat
Converting Bitcoin to Fiat is already an act of reducing privacy to your finances because you will need to give your bank details to other parties in able to process your transaction regardless if the exchange is CEX or DEX. But you're right that DEX like Bisq is the best possible solution for privacy seekers users to lessen the exposure of personal details.
I think there's no way to achieve complete privacy when it comes to this kind of transaction.