Reminds me of an online D&D.
Honestly, the two aren't even close to the same.
Questing follows the formula of "author writes chapter", then "leaves options to be voted upon by readers", then "author writes next chapter based upon these votes". It's really quite different from D&D. Although some quests DO incorporate RPG elements like dice and some sort of level/growth system, while others do not.
... Personally, I think it's all disastrously clunky, and only serves as further proof that all things decided by committee are doomed to horrific failure. MY advise, clearly, is "do something else". But it has a very real fanbase that obviously disagrees with me. Some of whom have accumulated years of wisdom evolved in the medium. So my secondary, probably more helpful, advice is to learn about the medium, since it's basically exactly what you describe.
I like this site. It has a questing dedicated subforum as well as a creative writing forum. I lurk thereabouts... a lot...
The users are possibly the nicest I've ever met on the internet. The mods are sane, reasonable, helpful, fair, and manage to enforce the rules they've set forth. Making them functionally the only place on the internet I've found that achieves this. I've seen 'enforces the rules', I've seen 'fair', and I've seen 'sane and reasonable'... but rarely even two in one place, let alone all three.
There's a NSFW section, but you need to create an account to see that section, so embrace or ignore at your preference.
Oh... and if you REALLY want "online D&D"... I've got an app for that, too.
Which follows the standard geekdom formula. Is good at what it does- which is provide a place to run D&D and other RPGs in Play By Post style. What it does NOT do is creative writing or good mods. Fortunately, the vast majority of the site's activity takes place in semi-private subforums that the Mods visit almost exactly never. Which is what makes the site tolerable.