There are two possible mechanisms that could produce a predominance of meetup posts over interesting new content: an explosion of meetup posts, or a dearth of interesting new content.
There are frequent complaints about how the meetup posts swamp everything else. I'm not sure whether anyone's come up with a convincing way to solve the problem and offered to implement it.
My impression is that there is less interesting stuff on LW than there used to be, partly because a small number of particularly high-quality contributors have moved elsewhere or run out of new things they want to say. Two obvious examples: Eliezer (more or less completely stopped; presumably he's working on some combination of saving the world and writing Harry Potter fanfiction) and Yvain (has no more time for blogging on account of being an overworked junior doctor; also blogging, more than ever but at slatestarcodex.com rather than LW).
Another explanation for the shortage of interesting new things: saying interesting new things is hard and more and more of the things people might want to say have already been said.
I'd agree that EY's stuff makes up a big chunk of the best of LW and Slatesarcodex is cool.
I'm speculating if LW has run it's course, at least quality content wise?
At some critical mass, it seems to me the content won't matter all that much in most groups. LW can function as it's own meetup.com where rationalists and/or Harry Potter fans can come to meet like minds.
It kind of reminds me of my time in church—it becomes not-that-important if all the doctrinal stuff is true because everybody benefits from the social construct in place as a distant result of once caring deeply about the doctrinal stuff.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.