I think the problem for me is I never quite know why I’ve missed a parry. Obviously it’s my timing, but I can’t “feel” the difference in timing between a successful parry and a failure. To me they feel the same, so I never know if I’m going to succeed or fail, and there’s no satisfaction in it as a result. I just hit the parry button and hope for the best - sometimes it’ll work and sometimes it won’t.
With Dark Souls, I almost always know why I’ve been hit. Usually I’ve gotten too greedy and tried to sneak in an extra hit when I shouldn’t, or I’ve misremembered the enemies attack pattern. But it’s generally very clear why I failed, and how to improve next time. I get none of that feedback from Sekiro, and because of that it’s just not fun for me to play.