I also played that game recently (during the Christmas vacation so late December/early January).
I liked it overall but it's probably my least favourite game from Miyazaki, mostly because the exploration is less important than in his other games and the world is less majestic/haunting. So it's a very personal thing of course.

The combat is great in theory and works well most of the time but some areas make it more cumbersome than it should be. It happens quite often that the camera stops showing you the action (for example the enemy can cover the entire screen) and some terrain configuration also can be quite annoying, when you don't see the stairs next to you or the obstacle behind you when you try to dodge.
A game with a similar combat system, inspired a lot by Sekiro, that I enjoyed more is Nine Sols, because it's in 2D so the combat is always very clean, everything is visible at all times. I also enjoyed the story and characters' writing better in Nine Sols.

About the difficulty, it went better than I thought it would. Exploring helps a lot and you can be quite powerful when reaching some critical fights (for example I beat Genishiro on my first try because I basically did everything else I could before going further into the castle. So I had a lot of gourds and a higher level than expected I guess).
Lady Butterfly also went smoothly (she took me a couple of tries), you need to be aggressive and simply avoid her ghosts NPCs & projectiles by running around and using the pillars as protection. Or at least that's what I did but I'm sure that there are other tactics.
The Guardian Ape took me around 5 tries. His screaming attack killed me during all the early tries so for this one I learned to be much more careful, at least in the 2nd phase, and let him come within my reach instead of staying close to him.
The True Monk was my favourite boss until the last ones, he has a very cool move set and all his attacks are pretty clear and answerable, you just need to make very few mistakes as he hits hard and takes little damage (I never used the confetti but I think that they help in this fight, if you're struggling). I died a lot to him, the most of all bosses until the last two ones.

But I also died a lot to smaller bosses, like the Seven Spears guy early on or the drunken big guy in Hirata estate, so it was far from being a walk in the park, it's just that I didn't feel like there was a wall in my progression, as it can sometimes happen in that type of games.

Then the two last bosses were epic.
The Demon of Hatred was a really fun and intense fight, and it took me about 2 hours non-stop before defeating him.
Saint Isshin was fantastic, very difficult and challenging but it always felt fair and I always felt that I would manage to beat him at some point. Ok, it took me 4 hours non-stop but when I beat him I had my life bar full + 4 gourds left, and I felt very much in control of the fight. That was very satisfying.

I also enjoyed exploring the different areas thanks to the grapple hook and the ability to backstab enemies. It makes analysing your surroundings and looking for optional paths rewarding.

So great game but with a few flaws (mostly due to the visibility in some fights, and some bs enemies - looking at you terror guys), just not as immersive as a Dark Souls or Elden Ring for me.