how about posting some in game screens or new Pokemon if there are any. Also when you post new info, you post it all at once which is a lot of text to read and a lot of people can't be bothered. When you posted the tour guide you could have posted a screenshot next to each area to break the text up. Also, your game isn't like the traditional Pokemon games as it has more depth and detail and maybe some people don't like that.
On a lighter note: People do seem to respond more when the word 'Beta' or 'Demo' is used but the quickest and easiest way to get posts seems to be...gym leader positions! Yep, that's right! People who never even post in most RM2K threads and usually have no idea what the game is about always want have a part in the game.