I am not a SAM main whatsoever, I just enjoyed it since Stormblood and play it as a fan of the job sometimes. Using Kaiten just before my big hits felt oh-so-satisfying and really added to the identity for the job for me. I actually liked Dark Arts in HW as well, hated it in SB, and enjoy the new SHB/EW DRK. I never felt like Kaiten (or even Eukrasia) was the same as Dark Arts. All three buttons felt unique and had different applications for use, adding further to job identity.

I imagine having a guaranteed crit on SAM's biggest hitter with Kaiten would've only made it felt even better. If enough people continue leaving feedback, hopefully SE will re-add it back.