@technomancy that's very insightful, thanks.
I think I agree with you. The Omelas story is very open-ended, and I think that's why I like it so much. It definitely does expose the hypocrisy and myopia of the reader.
We can feel high-minded and claim that we'd leave, but it takes a certain foresight to question the story in the way that you have just done. To realise that leaving is much easier said than done. To even decide that leaving isn't worth it, because it does nothing for the child.