How?
I'm not trying to get on your case or anything but I'm legitimately curious as to how he was "fine".
I mean, if you just enjoyed his Gundams and the surface concepts at play, okay, maybe that works? But it's really a problem when you realize you could completely remove him from the story and the major plot elements can survive completely unchanged.
Let me try.
I find Setsuna to have plenty of character growth throughout the series. He was a kid that got brainwashed into fighting a "holy" war and a self-made orphan. Under Celestial Beings wings he became a quiet, unattached soldier that aimed for a united world, one that wouldnt need kids soldiers like he once was. Season 2 showed him trying to grasp the true meaning of their mission while juggling overthrowing A-LAWS, protecting his friends/comrades, mourning and mulling over ppl he lost, and discovering his transformation as a true Innovator. The movie gave us a Setsuna that has grown accustomed to his new role as Innovator and person to fulfill Aoelia's master plan: preventing a war with alien lifeform (not with typical shonen kill-em all beam spam that ppl seem to hav preferred, but rather with communication and understanding).
To me, the greatest joy of the movie was seeing the Setsuna at the ending scene and comparing him to the kid that crashed Patrick Colasour's parteh :laugh:. He's come a long way. I understand that Setsuna is stoic, and always seemed to keep to himself, arguably inhuman at times but I didnt think it ruined his character. That's what he's always been: a soldier. He just found a better way to earn peace for mankind.
So yea, Setsuna from ep1 (excluding flashback): unattached soldier that only knows how to fight and lives only for the mission, Setsuna from the movie: a more empathic but still skilled fighter that ultimately chose to use feelings and (CAPTAIN PLANET) heart so that humans and aliens can coexist and end the bloodshed.
And if they ever did remove Setsuna from the story and the series can still survive doesnt necessarily mean that the character is at fault, rather it would be a testament to the durability of the story. It's Mobile Suit Gundam 00, not The Setsuna F Seiei hour. The one person you CANNOT afford to take out of the series though is Patrick Colasour (heads will roll if he ever left).
Personally, I loved 00 and am very interested in seeing AGE. Just letting the episodes stack.