Out of 98 episodes, only 37 involved a direct possibility of escaping the island. Of those 37, only 17 potential rescues were foiled as a result of Gilligan's actions. Admittedly, that's still a lot of rescues for one man to screw up, but the series also has a large number of episodes where Gilligan's actions save everybody - from death, enslavement, imprisonment, etc.
The bigger screw up was the Professor, who despite being a super genius, couldn't fix a damn boat.
And why the heck, if one was a mega Millionaire and another a World Class Actress beloved by many, didn't any rescue attempts come for them?!