What a way to give your opinion.
You compare two things that should not be compared, and would know that if you knew what you were talking about.
Kaiten was not just a button to increase damage like life surge is for DRG, it was a Kenki spender so the job gauge is not a mindless Shinten spender, but forces you to be mindful and don't screw up your next big hit.
Additionally, it's a 1s animation that was created to fill in the gap between the last GCD and the Iaijutsu cast. Just like when you use swiftcast for a skill, then cast the next one, you have a long time of inaction. Kaiten fell right in between to remove that weird timing.