I'd say that it can be used as a tool for doing all the things involved in the traditional literature sense. It is actually quite a handy tool for looking at extremes of any kind, as it allows you to strip away societal and biological conventions, and explore themes on their own. I realise this is not a common usage of the genre, but you took the example of dystopia as a good explorable theme, and then there are morality issues in Moon's The Speed of Dark as a decent example of what science fiction can explore as easily, and just as good as the traditional literature. Other facets of this is gender issues, which are quite commonly brought up. It seems to me that you are looking for some kind of radical aesthetics to be the norm for quality, as in things that question the norm, explore the themes that define us. I propose that these things appear in about as much genre literature as proper literature - it is just that the pointed focus in speculative fiction tends to sort away part of the issue. I find it interesting to compare to science, where such sorting is done all the time in order to produce something manageable.

Okay, now I am nerding out. I started thinking about whether one could make a statistical model to compare this, and whether or not the interaction between themes should be weighed as more important. Meh. I should not write stuff late at night when I should be sleeping - if it makes sense, it was probably not what I intended to write.