I think you missed some things.That's just off the top of my head.We see Chitanda's desire to be responsible and her frustration with her inability to get things done. We see that to some degree she envies Irisu's skills, and she attempts to learn from her. We see the humorous results of these lessons, and we see her own self-awareness of her limitations.
Don't confuse the show being about Oreki with the setting being about Oreki.
Hm... I guess i can buy that then.
I'm not. The show is pretty much about Oreki, how he interacts with other characters and how he has to be there for them. I'd say the show pretty much is about Oreki and his dealings in his life and other people's imo.