There is truth in this but it's also true the Sox have played 112 seasons compared to the Marlins 20. I certainly would hope that the Sox would have made the playoffs more often given that they've had 92 more seasons to do so.
The comments got me to thinking so I did a little basic math, hope the figures are right.
The Marlins made the post season twice in 20 years, an average of once every 10 years.
The Sox have made the postseason nine times in 112 seasons an average of once every 18.5 years. I did not count the Sox winning the 1900 championship because at that time baseball didn't recognize the American League as a 'major' league or the number would have changed.