Basically, this is why there are so many fandom RP's. They're easy to understand. Fans of the series don't need to know anything new, they just need to know the world they are already familiar with as fans of the series. Meanwhile, when a GM tries to pitch their original idea, it can be harder for players to grasp, because they don't know it as well. There's a small gap between a fandom RP and an overused trope like a high school RP in terms of "originality" and also how hard it is to grasp, but when you bring in more complex, unheard of ideas, that's when they're harder to understand. It's why "original" RP's are hard to find and fandom RP's fill up the boards. The former can be hard to pull of successfully, and the latter has a higher success rate.