Originality is the aspect of created or invented works that distinguish them from reproductions, clones, forgeries, or substantially derivative works. The modern idea of originality is according to some scholars tied to Romanticism, by a notion that is often called romantic originality. The validity of "originality" as an operational concept has been questioned. For example, there is no clear boundary between "derivative" and "inspired by" or "in the tradition of."
The concept of originality is both culturally and historically contingent. For example, unattributed reiteration of a published text in one culture might be considered plagiarism but in another culture might be regarded as a convention of veneration. At the time of Shakespeare, it was more common to appreciate the similarity with an admired classical work, and Shakespeare himself avoided "unnecessary invention". It wasn't until the start of the 18th century that the concept of originality became an ideal in Western culture.
I read much science fiction as a teen but got fed up with the limited imagination. The aliens were always based on some known species : octopi, lions, wasps, etc. and the social system was usually a thinly disguised Roman Empire. Sure, you can write good stories in that framework, but I...