Narratives

How do we figure out an answer?
First, we must admit that the whole thing must be based on speculation, but not blind speculation. We can marshal facts from the epics

There is another "story" that is not told: the mass army story:
the mass movement of the troops is completely and utterly ignored in Lang's telling

Another thing to consider: rage can fuel achievement: part of the wrath is that Achilles, already the best of the Achaeans, was turbo-charged by his wrath. That might be enough to explain the facts that Lang marshals to suggest that the wrath story was not really part of the war story: and if it is enough, then Lang's thesis becomes somewhat superfluous. The wrath story is but one warrior's story, one who burned extremely bright, accomplished a key part of defeating the Trojans (killing Hektor), and yet died before the end of the war. That might somewhat undermine Lang's thesis.

In the end, Lang's thesis is super-interesting and perhaps right: it gives one plausible answer for why Iliad is the epic and there is not an epic that tells the whole story or additional epics that recount other parts of the war.

Even if you do not buy it, it serves a great purpose: it highlights for us the many many echoes and reverberations and parallels between many heroes and their deeds, which makes the Iliad a highly wrought and complex work. It also highlights key parts of the narrative flow of Iliad. That there was a larger war story that happened all around the wrath story is surely true, whether or not the wrath story actually swallowed and incorporated the war story into itself as Lang tells it.