Since the 6.1 SAM change I've hardly touched it, and every once in a while I bring myself to play it in endgame content to try and give it another chance, and unfortunately every time it just feels so monotonous to play now.
In my latest attempt to try and convince myself that I can get over the Kaiten removal, I brought it to Tower at Paradigm's Breach, since I had such good memories of keeping uptime in the final boss fight on SAM with the color rings, knockback mechanics, etc. What I found was that...SHB/Lvl 80 SAM rotation still feels pretty good! Even without Kaiten somehow.
Turns out, having to use Meikyo Shisui immediately before every midare+Tsubame Gaeshi window worked out almost like a proxy/pseudo Kaiten in terms of creating the sense of buildup and release that Kaiten served.
Unfortunately, this principle can't really work with the current endgame/lvl90 rotation as the optimal rotation that we see in the Balance involves using a Meikyo Shisui stack for Higanbana, and using the remaining two stacks with a 2 GCD Yukikaze combo to get the third seal for your Midare. With this, there is no smooth buildup and release from the Meikyo press to Midare, it is interrupted and diminished. Feels like any other skill to press
Funnily enough, this observation could absolutely explain the divide between current dissatisfied SAM mains, and casuals who don't see an issue with Kaiten's removal, as casuals are most likely still using most if not every meikyo shisui stack to build up to Midare exclusively, therefore still preserving the intended job flow of slow buildup and release that Kaiten used to support, and still making each Midare burst feel good to cast.
This disconnect between the playerbases seems to be a result of dev oversight in not having comprehensive knowledge of how the lvl 90 optimal SAM rotation and how it affects job feel, eg. like how they thought adding another charge of Tsubame-gaeshi/Meikyo Shisui would make the rotation more flexible, but ironically for anyone trying to play optimally, it's just as rigid. In this case, perhaps they intended for players to mainly use their Meikyo Shisui stacks on Midares. But in optimal play, this is not the case.
But even then, even with all of the interrupting spells between your Meikyo press and your Midare press, Kaiten was enough to make it still feel good to cast. One could argue that it's our own fault for making the job feel worse by not playing as the devs intended. However, it's the devs' responsibility in the first place to ensure that the job still feels good when played optimally.
Conclusion? Pls just give Kaiten back.