Wow, I can't imagine myself master a game of such constant high-adrenaline fights that require learning, reflexes and concentration and even challenge myself more. All respect to you and anyone who does so

Are there any "trash mobs" in this game?
I also generally avoid high stress games. There's plenty of games with huge difficulty spikes that I can't be bothered to learn, from platformers to action games that are truly unforgiving.
But Sekiro is just an amazing balance of just accessible enough and complex enough combat system, that feels amazing to control and master (not that I master it or anything; but even being average, and once in a blue moon being great feels amazing).
With enough FromSoft's elements from their souls/borne games. With very nice exploration and a cool story, told in a slightly less obtuse way than their other games, but still leaving sufficient lore to be pieced together like a puzzle.
And yes, it does have a good chunk of "trash mobs" inbetween all the mini-bosses and main bosses. Since you do gain xp, and can grind for it, but you only use it to unlock skills and abilities (active and passive).
You unlock new tools for yourself, but the damage of these only increases in a very controlled way. Same as your general resistances. Only special dedicated items are used to improve your baseline damage and defense.
And you get those items generally by fighting bosses, or in the environment. Come to think of it, very similar to Elden Ring - Shadow of the Erdtree.
But bottom line is you can't grind for power. After a certain point you just need to improve your skills as a player. And those primary tools you use all-throughout the game, so you need to get good at them.
Most of all you need to get good at anticipating when you need to deflect, and that varies greatly from player to player. After 150h with the game I'm somewhat decent with it for most fights, but there are still plenty of them that absolutely kick my ass. Ones that I just can't seem to learn the rhythm of, and I apparently can't tell from their fast animations what I need to do. So for some I basically had to repeat certain fights over and over, until I drilled exactly what I needed to do, such that when it happens you can do it in a split-second. Which is, most of the time, the amount of time you have to react.
But shockingly, other players just seem to be naturals at reacting in time. I don't know how some do it. If they do constant drills themselves, or are they just naturally that good? You can never tell, and you always feel like the fights you see others take on and easily beat, somehow are next to impossible for you. It's a wild rush.
One other thing worth mentioning about Sekiro is that I don't think I've ever had such a love/hate relationship with a game so far. It's almost stockholm syndrome.

But every time I get fed up of failing, and ragequit, I leave it for a few hours or even a few days; and it keeps boiling inside me. Just imagining what else to try to beat it, and feeling I'm almost there.
And then failing again, and realizing you just need to drill the basics even more. You basically can't cheese or abuse the fights, more than what the game allows.
But after all of that frustration, once you get through it, you get a level of elation I've not gotten in most games. And right now, that I'm on NG+1, and am slightly overpowered, it's even more fun. This is basically the revenge tour. For most fights. Some are still as crazy as before.
It all depends on how the fight is designed, and some are just insane.
Anyway, as another update: I've cleared everything except for fighting the Guardin Ape, one of my all-time dreaded fights. This one gave me one heck of bad time the first time I fought it.
Will be curious how it fares, compared to the rest of them that I managed to easily get over. But technically this is where the hard fights start in the game. It's Guardian Ape and its rematch, it's Owl and its rematch, Demon of Hatred and Isshin. These upcoming fights will definitely break me.