This is how I feel.
The problem with Morrowind/Oblivion for me is that the games feel very superficial. Sure, there's lots of stuff to do, but when you sit down and think about them, all those tasks start to feel pointless. The games in and of themselves do little to convince you otherwise.
The problem? NPCs are lifeless. The world is empty. The story is lacking. The writing is bland. Oblivion put great efforts into improving this, but the result is ultimately the same.
How to fix the games without removing the open-endedness. The answer is pretty simple. Hire good writers. Make them work on the story and on the NPCs. Hire better designers. Make them comprehend that nonlinearity doesn't just consist of giving you two completely unrelated quests and letting you choose which one to do first. In fact, the answer is VERY simple.
What was the difference with the Fallout's, KotOR, or even Jade Empire. Even huge BG2? They all had at least semi-competent writing/stories, and they had at least a remote understanding of semi-multilinear design.
Though, it doesn't really seem that Bethesda is willing to admit they have issues on this front, so I doubt anything will be done. After all, Oblivion is their best title yet.