GrapheneOS is nearly the worst custom ROM you could use to achieve privacy, and Google Pixels the worst phones you could use to get away from Google.
GrapheneOS officially supports and encourages the use of Google Play Services and a Google account for “security” purposes. Their “unofficial” members also spread propaganda advocating for the same.
They are also an embargo partner with Google for security patches, and add features that may threaten the lives of privacy users, or end up in jail or death in certain circumstances.