I think this comes from the misunderstanding that 'a better world' means Utopia, where all the problems have been solved. Such Utopia is almost impossible to imagine, might be impossible in practice and is perhaps not that interesting to try to describe.

For some reason we have no problem imagining dystopias as something that can be a sliding scale of misery but utopia has to be something absolute - like a heaven on earth.

This is why I don't like the term utopia to describe what I'm looking for. Because people are always there to point out that utopia is something that doesn't exist by definition. Fine, so what do we call a fiction that realistically paints a world that is ever so slightly better? Anti-dystopia? Counter-dystopia?