It's just weird that a lot of these complaints on this issue are predicated on a "Halo 3 was an amazing story" angle, when it really wasn't. They aren't pulling an Aliens–Aliens 3-type "everything was pointless maneuver" here, Chief still saved the galaxy that time. This doesn't invalidate it, especially since the Halos and the Flood on them were always a remaining threat at the end of the game.