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There is one more problem i think - money. If a "good player" playing for guaranteed win - he plays with low skilled players that mostly play with little bets and don`t want to loose big money. What about tournaments? There's a buy-in which you have to pay whether you want it or not. I agree with oyu regarding cash games though.
In this situation a "good player" spent too much time for wining too small money. And playing in the tournament with good money he is playing against the same "good players" without guarantee to win.
Your win is never guaranteed, ever, you know this, right?
As of what poker player can be called a "good player" there's no consensus on this matter, but imo a good player is someone who can outplay most of the great players from the past, because they were not evolving during the past years, and thus have got their strategies outdated.