How is it really free and decentralized if most exchanges or brokers ask for your real lnfo like some kind of official lD or documents just to get some Bitcoin?
If you join a centralized platform, and it request KYC, you have to do it.
If you dislike KYC and value your privacy, you can choose decentralized exchanges for using.
If you want more privacy, you can trade in person and avoid connections with banks and bank transfer.
Do you see that privacy and anonymity you get, depends on not only Bitcoin blockchain, wallet and also how you practice your purchase and sale.