I think KYC is not that bad. The main purpose of it is for added security and protection not only to your account but specially to the exchange itself. So they could prevent from being used, intentionally or unintentionally, by criminal elements or money laundering activities.
Nowadays all the data's are collect and sell it on private companies so many peoples are not ready to join KYC exchanges but KYC is increase the security level most of the investors are understand why they ask the KYC verification.
It is limit the scammer so we should believe 100 percentage on KYC exchange.
I wouldn't trust all of the exchanges and give them my documents just like that. There are so many scammers and those exchanges can use your data for their own use or sell it to those who needs. I trust only few exchanges on KYC stuff. One of them is Bittrex.
Btw BitMEX has no KYC, but it's also smell fishy despite highest volume of BTC trading