There's a myriad of reasons why I think the older members seemed have dropped off the Escapist forums.
Firstly, there's the zeitgeist shift from this site being an uber intellectual gaming forum, to plain ol' gaming forum. Though this happened over the course of many years
A lot of us got banned in the 2009/2010 March Mayham for giving Zynga fans nothing short of hell when they came to cheer on their team. Which was kind of understandable when Zynga's boys did nothing but write low content posts and greatly upsetting the Mayhem with their spam-voting of Zynga.(It got to number 2, IIRC beating legitimate developers like Infinity Ward, Square Enix - the intellectuals HATED this.)
After that, the Mods were keen on keeping order and not allowing another Mayhem like that to happen again. They tightened up the posting rules even further than normal - so now a lot of people, including myself are a little afriad of posting anything controversial. Controvesy is the life-blood of debate (and flaming alike) and with debate dying down, the intellectuals were unintentionally being weeded out with the flamers and the trolls.
Then there was the mess to do with Game Dogs, which was a show put on by The Escapist's staff which the user base seemed to hate. People bitched about it with a passion and got banned for it. While I never saw it myself, the sheer number of people moaning about it put me off. The sad thing about the bannings, was that most of the people bitching about it weren't being abusive - at least to me, anyway.
I also don't know if this has anything to do with the drop off in intellectuals, but main articles had dwindled quite soon after, starving the intellectuals of moot things to discuss further.
A while later, Extra Credits came along. This was a valiant attempt to win back some of the intellectuals, if it were given a longer run - it would have worked. However, there was some big pay-dispute between them and the Escapist. As a result, they got the boot. Taking more people with them, who then went onto Penny Arcade to follow them.
Shortly before the demise of Extra Credits, a new show comes on - the Jimquisition. To say it polarised opinion would be a huge understatement. At this point, there were only a few die-hard intellectuals left on the Escapist. When they saw Jim's show - which they saw as an insult to their intelligence - they written into the forums to moan about it. To them, it was an abrasive, over-bombastic and reactionist show free of the wit and dry charisma that Yahtzee had.
Inevitably, when people shown their displeasure - they were shown the door. A lot of them left for essentially not being allowed to ***** about things like they were once allowed to do. Now I only see Crudus and Therumancer these days. (Those guys totally rock!)
So let this experience make you wiser, if you have an intellectual fanbase - don't neglect them. They keep you better than the competition.