That assumption is only true if there is no manipulation of likes. I believe that the presence of bot farms has been extensively documented by now, which should disprove the usefulness of likes on any social media platform nowadays.
You are making lots of assumptions when evaluating GitHub projects that you aren’t writing here.
GH stars can indicate: which of many forks of a repo might be the most active, which of many projects in a category might be the most used/trusted, the growth trajectory of a projects (stars over time).
No and no obviously, they dont target some desperate addicted teens