Very few stories are truly original....
Honestly 99% of writers of content are basing their work off of a variety of influences.... movies they've seen, shows they've seen, books they've read, history that inspires them, current events, etc.
Sure if your story obfuscates the influence well, and the story captures the imagination of the consumer well enough, it may be considered original.
Star Wars... people had not seen something like that, but the story isn't all that original.... it derives alot from history and religion:
In the end the story, like most, comes down to Good vs Evil, Light vs Dark....
Game of Thrones... love the story.... also love Dark Ages/Medieval history.... RR Martin clearly rips much of his world from historical time periods.... the level of technology, the feudalism, heck even the incest and forced/arranged marriages.... the politics and backstabbing....the contention between religion and crown.
But throw dragons and ice zombies, and some magic into it and kill off good-guy characters whom people expect to carry on to the final Good vs Evil struggle and people won't even notice you're converging on much the same Good vs Evil, Dark vs Light, (Fire vs Ice), endgame that countless stories have, and people will call it original because of how you used the unoriginal story components they've seen a hundred times before.
TL;DR
Not much story is fully original any longer, writers mostly have to just obfuscate all the common pieces so you don't notice them, and trick you into seeing something original, which is still really cool.
