Aside from the story itself, the problem is that, again, the player is removed from any urgency or any of the action. The player doesn't technically get to be the one to defeat the Didact. Cortana's really the one who stopped him, and all you as the player got was a quicktime event. Really lame.

: I missed a lot of the response to Halo 3, was there really no one that
: reacted that way to him surviving the fall to Earth?

What? Seriously what, I don't understand what you're referring to.

: Why does it matter?

Read my other reply. It matters because, like everything else in this game, we're removed from all of the action and consequences. There's no urgency and thus no real impact, and then our enemy falls within the simple matter of a quicktime event.