I mean sure, my Danganronpa RP is, of course, a Danganronpa RP. I mean it has a lot of differences that fans will notice, but it has 1 cannon character and lightly touches on the lore. 

I play in an RP that's all about magical girls. Doesn't really rely on any type of IP. Just some random city in America loaded with magical girls and the occasional magical boy. There are dragons, gods, cosmic horrors, aliens, etc. If that sounds farcical, that's CYOA RPS for you. It's original, but magical girls aren't. The idea of characters having powers attuned to an element or force is also 'unoriginal.'

Ultimately, I think people use fandoms because it's easy to communicate an idea. I can say "Hey, I've got an anime RP where you can be ninjas, b-but the ninjas have magical powers and get into big fights!" or I can say "I've got a Naruto RP, come look." Problem is you can't really talk to people about your RP in the topic title very well. Both RPS I've described have been going for about 3 years now, so I don't really look at the rest of the forum much.