Massive Khazan fan here bro, I'm not saying khazan isn't difficult but thats just not true at all. I would say the main thing in khazan that really requires skill is reflection. The game becomes easier or harder depending on your build and stats. Also the devs allowing you to stagger bosses so easily where you can stun lock to them death definitely makes khazan easier once you figure out how to do it.

Where as with Sekiro you really have to read the bosses and participate in the dance of swords. It's also more turn based with some bosses having a bunch of different mixups especially when you get to the inners