By definition, the main character (usually the Player Character / Warrior of Light) should be the center of attention. We've had a significant role in every story so far, and the overall narrative is framed as being their story. The story they were least involved with was Heavensward; that was Alphinaud's story with Estinien as the deuteragonist, and even then it became personal after Haurchefant was killed.
Dawntrail, in comparison, feels like it was written and then a few dialogue options were pasted into the script to give us the illusion of narrative purpose. You could cut the Warrior of Light (and hell, the Scions in general) out of the script and it would work just fine with a few edits. Even in our bread and butter capacity of being an indomitable soldier capable of handling threats nobody else can, Wuk Lamat upstages us at the very end. It's fine as a story, but video games are an interactive medium; being reduced to a hanger-on for an NPC isn't exactly most peoples' idea of a fun time in that regard.
The Warrior of Light should be the main protagonist, or at least have a significant role in the story. In Dawntrail you could replace them with an NPC or cut them out entirely. Kind of an issue, in my opinion. It's not altogether uncommon in Daichi Hiroi storylines, so I kind of expected it, but I wasn't expecting more or less every other character to spend most of the story warming the bench for Wuk Lamat.