i don't think you can count exchange as part of the defi ecosystem, unless you mean dex. i mean, cex is by nature centralized. there is no 'defi' about it. it's similar to forex trading, just that you trade crypto instead of stocks and the others.
That’s right, I can’t quite imagine binance exchanges being decentralized. We know we don't hold the keys to our wallet there. So whatever hack takes place, there is a high probability that the money of all who stakes o trade will be affected.
Dex or Dapp, on the other hand, are the ones referred to as decentralized when it comes to exchanges that require us to import our wallet.