Most of the fandoms I like. They aren't hard to find people for, they just never pan out or aren't exactly what I want.
First is Legend of Zelda. This one's complicated by the fact that I don't typically want to do canon characters, and that's what most people want. I just like the setting's feel and tone, and want to use my own characters and tell my own stories in it. Also complicated by the fact people usually want to play off a specific game (esp. BotW lately), and while I love all those, I really want to do my own take, without ties to a story I already know.
Second if Pokémon. This one, it's more... I think deep down despite loving the games, it doesn't actually work as anything other than a video game. There's too much I find I dislike when trying to translate it to written stories.
And usually, anything superhero-related I want to do, since there's several things I want in them, and they never seem to come together.
I had one way back with a handful of other people. It was a collaborative setting and we each created bunches of characters, heroes and villains alike, and each had our storyline contributions... But we all got busy, they got out of rping, and I've been left trying to recreate that. It's not most people's thing though.