Comment by SkyBelow

Could it be that stars were a good proxy, but as people realized such, they started being gamed, resulting in them becoming a bad proxy? Goodhart's Law would seem to always be in play for any proxy, because once it is recognized as a good proxy, bad actors will begin gaming it. A proxy that can't be gamed would be ideal, but I feel that is akin to wishing for the Philosopher's Stone.