Context is important here. Yes, 9 teams have more, but 8 of them are the original National League teams which date back to 1876. The American League didn’t get started until 1901, and among those teams, the Sox trail only the Yankees (who also are behind the NL 8). 25 extra seasons is a lot of games.
Percentage wise, the Red Sox are 5th, behind the Yankees, Giants, Dodgers and Cardinals.