No, it isnt. It would be highly immoral and unethical to call a project private and secure when using hardware that fails to provide either of those things.
Google pixels are the only devices that support the hardware security requirements. To use anything would sacrifice security, not the other way around.
You have chosen to ignore the goldmine of genuine issues with google pixels, of which GrapheneOS acknowledges, to instead attach a bunch of buzzwords to something you dont like.