No, you're free to try your luck in each of our forums. I'm just warning you ahead of time that the nature of your endeavor would be different for each forum.
Hentai Discussion: you would be analogous to an Italian immigrant arriving in New York City in the 1890s. The community has already been established for you. To use the analogy, the trees have already been cut down, the roads laid, the buildings erected.
Anime Discussion: you would be analogous to an American pioneer heading out on the Oregon Trail in the 1830s. You're headed for the wilderness. You might be the forefather of a great city like Portland or Seattle, but it falls to you, as one of the few people in this strange new land, to get the ball rolling. Think of it like Field of Dreams: "If you build it, they will come." In Hentai Discussion, the baseball field's already been built. In Anime Diacussion, it hasn't really. Several have tried but none have succeeded.
Personal advice:
(1) Discuss currently-airing shows. You did do this and it didn't work out. It was still a good idea, and I'd still encourage people in the future to post about currently-airing shows rather than famous old ones. Most people are more willing to discuss what they're watching now than to re-discuss for the 18th time a show like Cowboy Bebop or Neon Genesis Evangelion.
(2) Discuss shows which have a large fanbase which you also enjoy. Again, you did do this (with Bleach), and it didn't pan out there, but try again. Unfortunately, there really isn't any show airing right now which has united a significant chunk of the fanbase.
(3) Supply pictures! Pictures always help your cause. People are lazy by nature. If they even bother to read your thread but they don't think the show sounds interesting, then they're done investigating it. Case closed, on to the next topic. But if you include pictures, it could change their mind one way or the other. Great art. Pictures which capture some of the funny, scary, or tragic events in the show. Etc. Just be sure not to include significant spoilers!!
(4) Never invite people to "just talk" about the show. That's too vague. Paradoxically, people are less inclined to talk when you open the floor to any topic. They're more inclined to talk when you give them a specific topic. So instead of saying, "Hey, let's talk about why we like Bleach," you could start a thread off by writing things like:
- "When do you think [so-and-so] is going to die?"
- "Who's your favorite character?" (tired idea, but still better than a blank invitation to discuss the show)
- "Which was your favorite episode so far? Why?"
I dunno. I'll give you a specific example with Minami-ke: "Why do you think the first studio was not given the contract to do Season 3 when everyone seems to agree that Studio 1 is better than Studio 2?"
Maybe I'm wrong. Maybe people disagree. But these are just my own thoughts.