As to the Extended Cut. For me it did enough.
It made each choice feel like more than a colour filter over the ending cinematics, the voice overs really helped in giving the endings a unique feel. Yet it still maintained what Bioware wanted to do with the endings.
Which is the worst thing I can say about the Extended Cut. Why on Earth was this not what the game shipped with? People still may not have liked the endings if they were of this quality originally but there wouldn't have been anywhere near the fuss, people would have at least been able to look at the endings and think "well, at least they put the effort in."
The original ending is what Bioware wanted to do. The extended cut is a compromise between what they wanted to do and what people needed to like it.
The original ending fits perfectly to the structure :
-first, the whole structure (in the macrostructure, the trilogy, and in the microstructure, Mass Effect 3) is more like a spiral (2/3, with an acceleration in the third part, and it goes faster and faster).
-second, Mac walters and casey Hudson talked about the high level of the catalyst scene. This notion is very important to understand the ending. When people refuse the "high level" (I'm not talking about you, I actually don't know what you think about it), it's the whole ending that they refuse. The catalyst scene is supposed to be a higher perception of things, which means that we are no longer in development of basic explanations, that's why the ending is based on implicit and paradoxes. It had to go against our perception of things. And it had to stay on this higher level, not to go back on the human scale of perception, that's why the narration goes higher and higher till it gets to the meta level (the stargazer scene with the idea that the game is a story told by someone).
-third, the writers and developers are not the stupid guys some people here want them to be. They know what breaking a cycle means. The cycle is determinism. But they also know that narration is determinism (when you tell a story you force the audience to follow you. Bioware know that when you give a choice, there is actually no freedom, you force the player to choose a path that was created.). So breaking the cycle is supposed to be creating freedom. But freedom isn't determinism. So when you impose a narration and the player is supposed to be free, there is a contradiction. That's why most of the (good) stories about breaking cycles do not have epilogue (I used snowpiercer and Bloodborne as very good examples). That's why they wanted "speculation for everyone", because they know that the game is a personal experience and the apex is the final choice and the consequences.
That's basically why the original ending had this form. Sure, because it goes against the habit of reading of most people, it created that reaction from a lot of people.