Ah, the meta humor
Yes, the Dennis the Menace joke was an early sign of that. They started to rely on that a lot during the transitional seasons (9-12). It culminated in that abysmal season 11 episode where Bart got a race horse. Comic Book Guy's line about them repeating themselves could not save it.
The last two episodes of season 7 parodied the end of the grunge trend. Unfortunately, the end of the Golden Era was almost near.
But I still think season 9 had some very funny episodes.