When it was first learned that the Citadel was the catalyst, I thought "really? well, ok. Guess they are using the Citadel for some sort of climactic battle (though we did that already in ME1)".
Then I'm told that the Reapers have learned that Citadel was the catalyst and they had already moved it to Earth. I groaned a bit there. Why didn't they just destroy it? Why move it to Earth of all places? And they did it, just like that? No fight at all? What happened to everyone on the Citadel? It seemed kind of lame, but again I figured they just had planned on a climactic battle and wanted to use the Citadel, so, well, somewhat lame but if I get a good final battle, then OK.
Then I get to the last phase on Earth and all my team is there. I figure, cool, this is where I can rally the troops for the final big battle. Then it starts to become clear that is not the topic of my conversations with them. I start worrying that BW has gone all nihilistic on us at this point. I start worrying that the end of the game is not going to be satisfying at all. I start thinking that I have been boxed into a single ending because so far none of the plot diversity that I expected to see, based on my past decisions, seem to have occurred.
Then it came to a screeching stop. Suddenly I'm hit by a laser beam and I've lost control of the game. My first thought is "how come when I got hit by the laser beam on the Quarian home world I died, but now I seem to be walking around?". Then I discovered that I was, in fact, in a boxed in ending. I had only one choice of actions to follow. Then I see the kid-god and I'm thinking this has to be a joke. There must be some way out of this, if I go look for it. There must be some sort of climactic final battle, right? He gives me three choices, and that's it. Then all three choices turn out to be basically the same at which point I know that I've been suckered by Bioware.