Okay, I'm going to sound all hipster for saying this, but I think the reason you don't see quite as many big projects for Oblivion or Skyrim as you did Morrowind is because of the console crowd.
Now now, I'm not bashing Bethesda for the chocie to consolize the series. I love Skyrim and Oblivion too. But you have to admit that doing so attracted a different crowd than before, even to the PC version. And this lead to a new breed of people looking for mods, making mods, and (worst of all) JUDGING mods. I have lost count how many times a large project for an Oblivion mod fell apart because their forums (or their thread on the official forums) were flooded with all kinds of people bitching constantly and most unfriendly-like.
I'm not calling out all of the console fans. I know that the ones causing problems are probably in the minority. But minorities have a habit of being very, very, VERY vocal.