This author of the passage attempts to further define science fiction by comparing it against the myth genre. While both of these genres use estrangement as a literary device, science fiction uses this device in a different way.
Here, estrangement refers to how both of these genres address problems, societies, and character types that are present throughout all of history. Here's the difference: In myths, these types of problems, societies, and characters are forever occurring. There will always be people and predicaments like the ones that exist in any mythical story. Myths are heavily connected with archetypes, which are very typical examples of a person or thing. These archetypes are unchanging. The characters, plot, and setting in a myth are based on unchanging principles.
This contrasts with estrangement in science fiction. Montaigne's quote (in French above) translates to this: "constancy itself is only a more languid movement." This means that even with estrangement, this seeming timelessness, there are inner changes that occur. These changes may be era- and character-specific.
This makes sense considering how science fiction addresses the present and looks into the future, whereas myth looks into the past. Basically, the myth is based on fixed properties that are supposedly apparent in the world we experience, but science fiction is not fixed. It is a genre of exploration that forces the reader to look deeper. This is what the author is referring to when he brings up the "cognitive view."