I love all these people saying "Kaiten is just an animation."

Kaiten is the whole POINT of managing Kenki instead of just dumping it all on Shinten. You needed to balance the bar enough so it wouldn't over-cap when you Hagakure Dump on your filler or ready your Yukikaze boosts, but you needed to keep some on reserve because you needed to Kaiten your Iaijutsus. Hell, in AoE Kyuten barely ever came up because the area combo barely generated enough Kenki for it to be left for Kyuten because you needed to Kaiten your Tekka Gokens (And I personally think THAT is the reason they're axing Kaiten, because they can't make it work on AoE even giving us more Kenki and this expansion is focused on AoE for some reason.)

Without Kaiten there is only ever the decision to Shinten as soon as you get 25. Because you COULD save your Kenki on buff windows, but during buff windows you're kind of trying to throw all your Namikiri and Kaeshi stuff with at least one Hinganbana in there, so a lot of casting which means little weave windows to even throw 100+ worth of Kenki on. Not to mention you start your big buff window getting 50 Kenki, so you don't want to enter the buff window with more than 50, which means you'll be dumping your Kenki violently on Shinten anyways.

Kaiten is the only reason why you still balance your Kenki anymore now that your Seigan is gone (Which was a terrible thing to do, by the way, Seigan was awesome please bring it back.) It's not just "A superfluous skill with a cool twirl animation", it's a constant mechanic you have to play around in this class!