The reason Monero's got strength in privacy's because XMR doesn't connect funds so if ppl used XMR from centralised exchanges they'd lose anonymity. It isn't recommended to swap there but if Monero stays on decentralised exchanges it's going to be swapped. If bitcoin can't become a privacy coin ppl will use Monero.
If you receive XMR from a KYC exchange, they don't know who sent it to you, only that you received XMR. If you send XMR from a KYC exchange, they will know the address you are sending it to & the amount, but nothing beyond that. They really have no idea what you are using it for unless they ask you and you tell them.
I'm not sure there's any "decentralized" exchange for XMR. Maybe AtomicSwap supports it but I'm not sure, and they've had troubles recently. ThorSwap doesn't support it at all. There are only KYC exchanges, non-KYC exchanges, and swapping services (a mixture of KYC and non-KYC).