Right as many of you have said, I'd never pretend that Vaan's the main character, and the fact that he's pushed as such is FFXII's biggest flaw. That being said, I do appreciate the unique perspective his story has. One of the shared things FFXII has with FFT is the disenfranchised common people who suffer at the result of war. I'm not saying Vaan is anywhere remotely as sympathetic as The Corpse Brigade/Death Corps, but I like the fact that it's a primary focus of the first third of the game. It's a really mixed feeling where I liked following Vaan's perspective even if in the long run, Vaan's a bit player. Like, when the story treated Vaan as a protagonist, I honestly believe he's a pretty solid protagonist. Nothing ground breaking, but he's has a clear arc with decent pathos.

I guess to make an analogy, one that's really only gonna make sense for Hip Hop fans, there's a distinct good kid, mAAd city narrative to Vaan's journey (it's a common Rap narrative, but GKMC is a modern example), at least as close to that kind of narrative as a T rated Fantasy JRPG can get. Like Kendrick Lamar:

-Vaan starts poor and gets through the day rocking a false set of bravado. He makes destructive decisions (robbing and picking fights with imperials),
-Daydreams about being a big-time celebrity (a Sky Pirate rather than a rapper, both are shown to be equally glamorous and of equal notoriety) despite the nagging of his family-figures.
-He gets in over his head in an event that causes him to rethink the trajectory his life is headed (Vaan goes to jail and Penelo gets kidnapped, while Kendrick's friend dies in a shootout).
-With new resolve, Vaan uses his new connections (Clan Montblanc and arguably Balthier's mentorship, for Kendrick it would be his record deal) to not only transcend his socioeconomic status, but also struggles to improve the community, with Vaan taking hunts and playing his part in restoring Ashe to the throne, while Kendrick forgoes commercial rap in favor of writing about his experiences, and giving back to the community.
See also: CREAM or Life's a B**ch

Like, I know that's the framework for a common rags to riches story, but I like it a lot more than the standard "Vaan is a poor man's Luke Skywalker" comment I see EVERYWHERE. Luke is a farmboy who goes on an adventure. Vaan is a war orphan who manages to escape a life of poverty.