Throwing my 2-cents (my 2-sens!) in as someone who started getting serious about sam a week before shadowbringers launch in the small hope that it reaches the ears of the dev team: Please give us back Hagakure!

Hagakure as a cooldown introduced a bit of ebb and flow to the job when it came to kenki management. If Hagakure was still far away from refreshing, you would play conservatively to make sure you have the kenki to boost a midare or higanbana (or both in quick succession). If you knew Hagakure was going to be off cooldown by the time you have your sen, you go nuts spending your kenki, switching from a build up and blow up style play to a frenzied constant-weaving style of play. It created some level of flexibility in how you could play if you understood what gives the most bang for your buck. As others have said, it also lets you dump your sen for phase transitions. You can use it to dump your sen if you want to refresh your higanbana (and gives you the kenki to boost it).

The new ikitoshin is just kind of their, kind of brainless, and doesn't really enhance the gameplay beyond "use this to shinten some more". Or syncing it with the 50-kenki spenders (gurren and the new one) so you can always use those attacks.

The new samurai set-up just seems kind of stiff without Hagakure to me, where we're always building up to Midares (and we can do a second Midare every minute now). No real feeling ebb and flow. I think it was durring a live letter they mentioned the reason for the change was because dumping sen feels bad? I can't agree with that idea at all. I love dumping sen, or that is to say (and I'm probably repeating myself) I love the ebb and flow, the give and take of the job.

Those are my personal feeling as someone who more recently took up the katana before Shadowbringers anyway.