...but Gilligan's crew couldn't get off it? Well, if you want to get technical, Gilligan (perhaps the largest single impediment (https://tvtropes.org/pmwiki/pmwiki.php/Main/JustEatGilligan) to their being rescued) was the “crew”; the rest of the group were passengers.

made for a sitcom ... +-

...but Gilligan's crew couldn't get off it? Well, if you want to get technical, Gilligan (perhaps the largest single impediment (https://tvtropes.org/pmwiki/pmwiki.php/Main/JustEatGilligan) to their being rescued) was the “crew”; the rest of the group were passengers.

I think it was because they lacked faith that their predicament could be solved. They accepted the hopelessness of their situation, and their resignation became their biggest barrier.
Plus, you'll notice that none of them was really suffering, there were no looters , muggers, or thugs to want to get away from....the few times that bad influences found their way into the neighborhood, they were sent back where they belong in short order.

The island was a utopian dream, and the show was a satire about people being too ignorant to know when they have got it made.