A games rating system goes from 0 (bad) - 5 (average) - 10 (great) for its time. If you're gonna rate games outside that this whole system falls apart and is meaningless.
You not understanding how score aggregation or reviewer score bias works or not understanding that the numbered scoring system is arbitrary isn't going to make the game be over average.

Just look at the score distribution in opencritic. Scores aren't distributed uniformly no matter what you think about them.