The problem with graphene is that is shamelessly promotes proprietary software.
How does GrapheneOS “shamelessly promote” proprietary software? I don’t think I’ve ever seen them do this. Maybe you’re referring to Sandboxed Play Services? But that isn’t “shamelessly promoted” or recommended, it isn’t even included in the OS, its just an optional app that can be installed for those who need it.
They have build tools to try to make it safe to run non-free programs (proprietary software) but that entirely misses the point.
I assume you mean Sandboxed Play Services again? That’s far from the only feature or benefit that GrapheneOS gives. They do much more work than just Sandboxed Play Services or making it safe to run “non-free” programs. They make it safe to run ANY program, regardless of license.