Regardless of whether or not you provide your own SSL certificates, cloudflare still uses their own between their servers and client browsers. So any SSL encrypted traffic is unencrypted at their end before being re-encrypted with your certificate. How can such an entity be trusted?
My take is: Any data worth your while shouldn’t just rely on HTTPs anyway. You should have more layers of encryption. That’s how majority of the companies do it.
And for people who do not even know this, are better off using CF as MITM.