Colossal Failure was a not-so obvious over exaggeration. The game is obviously fun and I've played it a ton.
But in respect to what they advertised the game as over the past two years.... then the product that we got. I don't buy it all changed because they ran out of time.
Then I respectfully disagree.
To supply a bit of evidence, I'll list a few things from the past that Bungie also talked about, but cut from the end game.
Halo 1
The end warthog sequence is supposed to be on a giant forerunner structure, not the Pillar of Autumn.
Several levels are repeats of previous levels either running the opposite direction, or a day/night swap.
Halo 2
A boss fight with the Gravemind was supposed to be the end of the game. Pretty much most of the story from Halo 3 was supposed to be Halo 2 originally. The ending, of course, being the dead giveaway.
Halo 3
There is literally an entire sublevel that has no enemies in it, and only acts as a long hallway into a mission end cutscene.
There was supposed to be a lot more going on in High Charity, and the Cortana level is actually what was supposed to be at the end of the Flood level on earth.
Halo ODST
Literally half the map was copy pasted:
http://i.imgur.com/84NDYIl.png
Halo Reach
https://www.youtube.com/watch?v=l7gww5l7edY