If you are technical and want root its very easy to patch a build of GrapheneOS to include whatever mechanism you want. You can even automate this to continue to receive updates.

I think the decision of GrapheneOS to maintain the attestation features and not providing user root is what gives it a fighting chance of being accepted as legitimate 3rd choice. See: Revolut and others adding GrapheneOS keys and trusting their attestation

Like or not, for most users, having root access is a liability, especially with more and more important things being held on phones . Someone downloading a photo editing app and then having a rootkit installed in the background that waits to empty their bank account is not a workable situation.