Again, I want to make it clear that I'm only talking about the unemployed people of this cast, not people in general.
But you're right, there could be a whole other reason for these contestants' unemployment. In fact, Mahsa wasn't fired for her personality and was fired for another reason (in her case, it was simply appearing on the show).
With people like Stephanie, I would think there's another reason for their unemployment. Poppy even said on the show that she simply couldn't find any job openings. But with people like David, I tend not to give them the benefit of the doubt. Who knows, maybe he wasn't let go for his personality... but yeah, with the way he's portrayed, I doubt it.