I've actually thought that trying to get users from non-imageboard websites onto smaller imageboards might be a good idea, but then you basically have a bunch of social media using, emoticon :3 posting people instead of people who can conduct themselves well.
Its sad too, because without users places like Samachan will die.
You actually do bring up an interesting point though. I definitely think it's a fault of the community rather than the rules/site itself. Pretty much everyone is there for anime I think, so it does make discussion on other otaku things non existent. Which is a shame, because a site populated by people using both /a/ and /z/ could be a really good quality website, imo.