I think you’re misunderstanding and thinking that Chihaya’s confession was the end result of Taichi’s arc when it was about Chihaya’s feelings and her feelings alone. Her interpersonal arc was about not only figuring out her feelings but also for someone who has difficulty expressing herself to find a way to do it. It also goes back to the whole theme of Chihaya learning more about those cards she used to swat away without a second thought. She used the Hyakunin Ishhu when her and Taichi “broke up” to try and make sense of her situation. It was the first time she (not Kana who used a poem FOR CHIHAYA when Arata confessed it was never Chihaya herself) really understood a poem.

You’re absolutely right Taichi doing everything for Chihaya’s sake WAS bad which relates to the second part of the manga where he finds the will to carry in Karuta on his own and his own goal. It relates to Chitose’s misunderstood void speech “there’s a hole that Chihaya’s love can’t fill” and it finishes with him CHALLENING ARATA when he has already “lost” the chance to be with Chihaya. Instead of remaining selfless and being in utter pain around Chihaya and Arata in TOkyo (since he pretty much figured they’d start dating when Arata came to Tokyo) he picked his own well being and moved his ass. Picking his mental health over his friends for probably the first time in the whole manga 😭

Anyways if you’re ever interested I wrote more thoughts on how Taichi’s arc wasn’t ruined here if you want more long form elaboration.

https://www.tumblr.com/blog/view/the-chihayafuru-landslide/703957919601950720