I agree that AnimeGAF tends to be a bit of a walled community, but then again I'd rather have constant discussion of stuff rather than threads like JoJo's, where people post impressions for one or two days and then the rest of the week are the equivalent of filler episodes while the community waits for the next one to air.
And every now and then someone watches some old anime and their reviews prompt me to add it to my watchlist. Seasonal shows are a great starting point IMO, but it's always cool to see someone pick up an old show and talking about it.
Still, if you're looking for proof that AnimeGAF's a very small community you needn't look further than Cornbread's let's watch threads, which kept attracting the same group of members over and over, only in diminishing numbers after we got burned out by awful stuff such as Sunday Without God or decided to watch Mirai Nikki. I kind of miss watching shows and posting impressions alongside everybody else on a daily basis, but then again I guess things couldn't keep going once the turnout got too low.