I will like to point that Bitcoin decentralization is different from financial privacy.
Bitcoin being decentralised means no central authority controls bitcoin protocol
Anyone can hold their own private key without permission or make transactions while relying on a third party.
if the exchange company discloses the customer's personal information to an intelligence agency, an authority in the relevant country, or a scammer or fraudster, they can also use physical attacks to harm the bitcoin owner and try to snatch his bitcoin.
There are decentralized exchanges like Bisq
It doesnt have to be a centralised exchange
You can even try an exchanger like peach bitcoin though there's a limit before kyc is requested.
There are other ways you can work on your privacy like avoiding address reuse and not disclosing your data online.