Interesting idea, thanks for taking the time to elaborating it on here!
While I agree that stars on self-hosted forges are of higher value than something on GitHub, I’m of the opinion that we can come up with better, more human-centric metrics than stars to measure of a project’s popularity.
I have a few ides of such metrics, but they have more friction than stars. One of them is endorsement from fellow hackers: something like bookauthority.org but for software.