It certainly has some of the worst side cast. Lulu and Khimari can straight up be written out.
Brainlet take. Cutting Lulu only remotely makes sense if you think every character in the cast needs a game-spanning character arc or some do some pivotal action only they can for practical reasons. Lulu doesn't have either of those, but she adds to the group dynamics in a meaningful way. Imagine if Lulu (and Kimahri) weren't there. The party would consist of 3 kids, a dumbass, and a guy who keeps to himself. The group would have no one who could work a the "mature adult" to help keep the group functional.
Many scenes where she interacts with another party members would make less sense replacing her with someone else. Like when her and Wakka have a couple private discussions. Those talks only work because Wakka and Lulu are close and the young adults of the cast, feeling the need to look after Yuna and Tidus. Or the many talks Tidus and Lulu have over the game, where Lulu acts the "reasonable moderate" of Spira basically, not being fanatical about things like Wakka but still believing in the status quo, and she calmly explains things to Tidus so he'll act more appropriately, but in return this gets Tidus to think and question things that Lulu doesn't always have an answer for. It's notable how one of the only times she ever loses her cool is when Yunalesca reveals the whole truth at the end. You would expect something like that from Wakka, so it wouldn't draw much attention if he did it, but from Lulu it really underscores just how much the average person really held on to the false hope Yevon gave them.
She might not have a fancy personal arc that stands on its own, but she's important for helping make everyone else's characters stronger with how she interacts with them.
Kimahri actually isn't very important since he's too quiet and doesn't have any good relationship with the other characters outside really wanting to protect Yuna because of something that happened off-screen 10 years ago. Even so, I don't see how an FFX without Kimahri is nessicarily a better story. He doesn't detract from anything and there's a couple major scenes you'd have to write around.
In general, I think too many people are weirdly eager to cut major characters from JRPGs. It's like /v/ posters who take the whole joke about Tim Buckley working better with less words too seriously to where they make comics edits where they eventually cut it down to one panel without dialogue and act like they're improving it. I don't get why JRPGs in particular always get brainlets trying to insist half the cast is unimportant and could improve the game if they butchered the story down. You don't see this thinking with Western RPGs.
