Heavens, not by any means, "forever marooned." Just for a maximum of 10 years while we get another mission with a return vessel over to Mars. In the mean time, those men and women could establish a fledgling colony there with hydroponics, a rover or two, and ways to build housing with present materials. I'm not in a position to comment accurately about how long it will take them to establish the livable colony because I don't know specifically what provisions and methods of atmosphere production/recycling they're bringing with.

Think of it like a startup. PG once wrote something like (paraphrasing here), to prove that a startup will work, try to build the smallest functional subset and build from there. And launch quickly and iterate often.

After we get a craft to pick them up, we'll have a temporary colony that the return craft's crew can occupy.

Besides, if those men/women were not able to stand ten or twenty years of loneliness and hard work being colonists, are they really the right people to send on a mission to explore another planet?