"A novel is just a story." That is true, but it also is misleading. The "just" in the sentence is reductive. It minimizes the worth of "story," pulling it down to the stature of a joke or something else of scant merit. In fact, a story can be a mind-changer.
Story-telling is ancient. At first it was verbal, then representational and, finally, written. Stories are found in sacred tomes and secular tracts. They are leveraged by historians to revisit the past and crafted by visionaries to peer into the future. Poets tell them in rhyme or free verse. In every instance, a reader or hearer is changed, a little or a lot.
Dictionary.com defines story as "a narrative ... designed to interest, amuse, or instruct the hearer or reader." To my mind, the best novels accomplish all three. They grab and hold the interest of readers, instruct them through character development and experience, and leaven the learning with occasional laugh lines.
Storytellers ultimately are valued according to the worth of the stories they tell. That's how it should be. Singers are judged that way, by the songs they sing and how they sing them. Baseball players by their batting averages and ERAs. Preachers by their sermons. Lawmakers by their laws. Anything else is notoriety.
Therefore, story lines that novelists imagine and develop must stand on their own. Their characters live on in memory only if they touch hearts, inspire, or otherwise cause readers to reflect. If they are forgettable, they deserve to be forgotten.
A novel is a story. A good novel is a good story. There is no "just" about it.