Fortnite steers wildly clear of trying to mimic PUBG’s realistic gameplay formula, and instead strives for an arcadey feeling and varied gameplay. PUBG refines the Battle Royale formula that Brendan “PlayerUnknown” Greene had struck upon back in Arma 2, and so it’s quite similar to the games that came before it - it’s just a lot better.
Still, Fortnite isn’t a straight clone - in a lot of ways it’s more original than PUBG.