My bet is that EA is behind the dissapointment.
Let's get our facts straight:
1. Initially it was planned that there would be more places the player could visit like Omega space station,the Citadel Tower,and the Citadel Wards.These areas weren't included because the development team didn't had enough time,and that's because EA gave them littile time,and in that time they also asked them to make up a multiplayer mode,so EA could sell Online Passes...
2.The reason the endings where bad is because they where rushed.The initial script was saying that the Catalyst would be the last living Prothean,and the last gameplay section of the game would be at Illusive Man's base,where you would have a boss fight with the Illusive Man who is indoctrinated by Harbinger.The reason they had to come up with a new ending the last moments is because their publisher asked them to have day 1 dlc.So they delayed the game for 3 months,just to make up a new,rushed ending.
3.The paid day 1 dlc. Well it was day 1,and it was paid.But it was also the reason the endings where bad.
In the end we got a bad,rushed ending that didn't made sense,3 months of delay,day 1 dlc that was excluded from the game,and fewer
in-game areas and missions,because of EA.

At times like that I'm so happy that Bethesda is the publisher of its own self.
