Ignoring the fact that this finale comes right out of nowhere as the first 2 games weren't building up to anything of the sort at all, for a finale of a big saga like this was hyped up as, it's more interested in making you ask more questions than anything else. The story frustrated me constantly. Let's run down the list!
Alvis being the big bad all along is stupid, not only is he never mentioned in the base game by any Moebius, but him being rewritten to be evil is so out of nowhere and forced
I personally think N was a more compelling villain when he destroyed the city out of pure desperation because he was too far gone. Turning around and going "Actually he was trying to stop Alvis during that" kinda ruins it for me
Shulk and Rex are alive for...no real reason. At least, I wasn't able to make sense of it. Why did everyone else die but not them, is it because of Moebius or something? They did have a deal with Z
Having the main characters' kids be focused on so much here feels like bad fanfiction, especially because they barely have any character and are not interesting at all
Not to mention Glimmer's voice acting is next level bad
Matthew and Na'el are the only part of this game that I liked, they're arguments felt real and emotional. I really wish Alvis wasn't involved here because it just means Na'el is off screen for most of the game so 99% of her character is shown in flashbacks which kinda gets old
Was there any real reason for Alvis to move Origin right by Prison Island so the party could easily get there? I just find that funny it's so stupid
The ending, oh my lord. Talk about completely undermining the ending of the base game, and the fact that it comes out of nowhere too, it really bothers me
So basically all of Xeno3 amounted to...nothing, because immediately after the reset, the worlds merged anyway, fantastic.
I hope the Xenosaga fans are happy though!!!

So the story is a mess, but is it actually fun to play? NOPE!
This game goes back to the worst of Xenoblade 2's design, with bosses that can just end you in seconds when their health is low, making you do the 5-10 minute fight all over again!!!
Exploration is boring, the map is just areas from the first 2 games but again. It's even less interesting than the base game's world.
The game also gates you from progressing until you have enough ether cylinders which is just kind of annoying. Unlocking arts and gem/accessory slots can only be done by finding items on the map as well.
I understand that the game is giving the incentive to explore beyond the beaten path, but it just feels more like padding than anything else.
So yeah, I don't like this game, I find it to be an absolute mess, the worst of the series, beyond...Future Connected, I guess. I'd rather play Xenoblade 2 from a new save file than touch this again.