The ending sucks, you're indoctrinated, yadda, yadda, yadda. The wheel of ka keeps turning.
Taste the rainbow!
A newbie's guide: Why the ending sucked.
Why the ending sucks part deux
A Logical Breakdown of Why the Mass Effect 3 Ending Makes No Sense
What the ending could have been if Mac Walters was a competent writer.
"Yes, my sweet?"
"Who was Marauder Shields?"
"He was the greatest hero to ever live. He tried to save us from the greatest disaster our people have ever known."
Confused about anything else? Well, you should be, but check this out anyways!
Oh, and finally: The real ending of Mass Effect 3