Saber Marionette and OMG are still quintessential. I mean, Saber Marionette even discusses moe instead of just having it there, and OMG is definitely a high point and a tie-in to other nerdy and intellectual shit that correlates with liking moe. Maybe it's that people who consume moe are quickly bored, and the best works aren't discussed at the expense of newer ones. Look at us, we have an active thread for fucking Tooru the Magic Dragon Maid, but threads with topics are either inactive or stupid.
Then again, in person things are different. The common ground everyone shares is usually the classics (at least from mid-nineties onward) and it's easy to dive into an in-depth conversation of these works. I guess you can't really go "exactly! and even more, it's like this and that, too" here when you have to wait days for a response, if you get any. Do we even have a population of active and good conversants here? At least three or four are required to get anything going.
I didn't see K-on as interesting to begin with. The girls are cute but... I guess it ultimately lacked the depth of, say, Azumanga or Lucky Star. Speaking of Asumanga, do you guys remember Masamune Shirow? That guy put out some lasting masterpieces. Depth everywhere you step to the extent that reading his works is like walking in a swamp, at least until the third or fourth time. The latest anime with substance I remember was Cross Ange, and that was terribly articulated. Anime like that will be easily forgotten since nobody even picked it up when it aired. Kill la Kill is the latest really good anime, and it still gets content and discussion. The latter should get even better now that the edgemasters and perverts are looking for their next fix away from klk.