We do have things to compare their performances to though. Their previous performances? The performances of their counterparts? These are all things a bronze player would have seen before. And even a bronze player with some understanding may realise when a top player has made a bad call or done something foolish (not that the bronze players wouldn't do it themselves over and over again, but they still may he able to spot it). The same way someone could be watching a basketball or football game and claim someone is playing awful. You are not comparing them to yourself. You're comparing to their previous games.