Having slept on it for a bit, I think this episode is ready for another review.
I can see that the writer's were going for a 90's parody, but they ruined the episode by weaving in the Homer-Marge back story. While the time period in their lives is definitely episode material, it probably should be within the constraints of the time line, which would put it somewhere in the late 70
s early eighties.
Some of the jokes were decent (Sonic, LotR, the nerd being 'grunged' by the crowd) but others fell really flat (Back to the Future, Bill Clinton, the narcotics gag). And don't even get me started on Homer inventing grunge, I don't know what they were thinking with that idea.
Now correct me if I'm wrong, but The Simpsons was broadcast for the entire decade that was the nineties, during which time it not only influenced a lot in the world of TV and culture, but also transformed it entirely. I find it very odd, that said show would not refer to itself in some way, especially as it has done so in the past (Bart's balloon in the Thanksgiving Day parade for instance).
As a standalone episode, it is about average for the current times, but for fans of the show, it proves beyond reasonable doubt that the show in it's previous incarnation is perhaps lost forever.