I would say that one of the most important aspects of science fiction in the literature canon is to show the idea that there is always a more sinister and hidden side to the harmonious social order. I don’t see science fiction as the stereotypical notion of “green, bug eyed Martian” who approaches an “earthling” only to say “Take me to your leader” in some bizarre voice. This is certainly a part of the science fiction experience, but I don’t see it as possessing the most amount of value in assessing science fiction. In my mind, being able to read literature that probes the very value of our world, technological advances within it, and help to reveal the “other side” of what is present might help bring a new light to analyzing it. For example, Orwell’s vision of life in Oceania in “1984” could be seen as science fiction. The advancement of technology to progress to a point where internal thoughts can be sensed and controlled through mind-altering elements is something that is highly resonant today with such a dependence on technology. What if our modern dependence on technology helps to foster our own unwilling and unaware surrender of our own thoughts and perceptions? For example, what if the Internet was controlled by an evil genius of sorts? A big brother type of individual? Consider the possibilities of how horrific this would be. Science fiction helps to make this vision one that causes us to stop and pause. Writers like Bradbury and Vonnegut as well as LeGuin do this consistently in helping to make Science Fiction articulate a vision of reality that might not be as completely present on first glance.
I think that science fiction plays the role of the agitator in some ways. It is one of the few areas that authors are allowed to really play with things like reality and to expect readers to suspend disbelief so to speak. Because of this, science fiction writers are often pushing the boundaries of what is acceptable, what is "normal" and as such really help to expand the boundaries of literature.
It also serves, in my mind, as a foil to the ways that critics try to take control of literature in the way that they get to decide what is or isn't literature, but science fiction can be so difficult to decipher or to classify or break down, particularly because the authors may be doing things or writing about topics that are so far outside of the normal critic's range of familiarity, that it can serve as that foil.
Science fiction is like the geekier side of literature. Science fiction isn't analyzed the same way you'd analyze a Frost poem or Shakespearean play. Its not about diction and form, its about meaning and implications. Its about world building and social commentary. Science fiction can contain romance, thrill, suspense, and adventure which is what makes it such a hard genre to define. Such an expansive genre often seems to have no place in high school literature classes beyond 1984. But science fiction is as much about the meaning of humanity than any other genre.