These exchanges are running off of traditional programming, not decentralize programming correct? Isn't it possible to run them decentralized like with Ethereum

These exchanges are running off of traditional programming, not decentralize programming correct? Isn't it possible to run them decentralized like with Ethereum or something? Maybe that's too slow? Just wondering as trust mixed with trustless seems tainted by design. I imagine getting some encrypted thing passed with a one time transaction id to transfer from a real fund that when completed, verifies transfer and notes that in the blockchain. I don't know though, haven't done programming DAP stuff yet.