I agree, though I haven't left yet. I have curtailed my posting since early 2001 to almost nothing.
Reading the threads is not typically what I come here to do anymore. I rarely go past the article and 1-4 posts before I go back and select another one. It seems no one wants to discuss the article as much as they want to scream about it.
I'm new in the last 6 months.
My impression of this site is that the members do a fantastic job of finding great articles and posting them. I can stay on top of anything I like on this site.
The discussion is pretty non-substantive, though. I characterize responses as either short quips or rants. Like RedWing9, I pick the article, read it, and then maybe read 4 responses, and then move on. I rarely engage in the discussion.
I was part of another forum that went this way--lots of really great discussion, the site became more and more popular, and then it disintegrated. My opinion is that if the people who engage in really substantive debate leave a forum, there is no one left to show others what the forum is supposed to be.