That was originally my issue with it, the game was pointless in the end. But after sitting on it for a few months I'm starting to appreciate it more, the whole game in general really, still don't like the combat, but I'm warming up to the story, especially after replaying Gears recently. I suppose you could say there is something about the pointlessness of war or something etc etc.
XB3's effective themes are kind of meta in a somewhat non-obvious way, but meta nonetheless with how XB as a fandom developed and what it is trying to say to people as a whole. As well as talking about people in a broad way like XB1 and 2 did with proposing an optimistic idea that people need to just be willing to confront and talk to each other.
The basic idea I got is that everything has to end, and those who cling and force the world to just stall and stay the same because they say so are ultimately pathetic huskless people in a sad way which is why the consuls are "concepts" more than characters. As overdone as meta commentary is these days, XB3 doesn't just lecture the audience about how we're all actually moebius, but I think you can come to that conclusion if you sit on it for a little while.
The final boss is
effectively a different version of Klaus, just altered around some but ultimately has the same man becomes false god feel. XB2 had the fake god complex with pope man, and XB1's is extremely obvious. It pretty much espouses the idea that no man can ever truly control everything and be right. That no singular person can be an absolute authority. The synthesis of ideas and compromise being strong aspects of XB2's narrative given how Blades work and the whole "Everyone is fighting their own war" speech a while back in the early sections of the narrative that you can kind of see continue to play out throughout the game. XB3's compromise is effectively its ending as a whole.
The most common idea I find that most people come to with XB3's overall narrative is something something capitalism bad, or at least "the elite" are bad. Which in this case I think is justified enough of an interpretation given the parallels you could make with the image most people have of "the elite" and how the consuls and moebius work.
Barring all the usual commie sperging that comes up when people talk about how a AAA video game is ironically justifying why capitalism is bad, I think XB3's story has a more simple purpose in what it wants to convey with its ending that can apply to literally anything. That people need to just let shit go, that clinging to shit forever is just unhealthy. It stings and it sucks, but you got a whole life to live beyond that one moment. Kind of like how some of XB's fanbase super clings to 1 and just pretends the other games don't count at all when the game is over 10 years old now.
If Takahashi was really meta about it, he'd pretty much say at some point that XB3 is the end of his Perfect Works project and that he wants to make a whole new kind of sci-fi anime romp and just let himself make something else going forward. I don't know if he will, but that'd be a nice way to back up how I think XB3's story and ending is meant to be taken for the average person.
Pretty much I just imagine this was meant to be said to the camera at XB3's ending while some Redditor was typing up why XB3's ending sucked because Shulk wasn't in it enough. Though I'm extremely concerned about how they'll handle wave 4's DLC story with it hopefully not just being some pandering tripe.