Then we are not really talking about a genre but a specific target audience. If you narrow down that much, then just list a few games. I don't play this kind of games, I don't know why some people would play them and I don't really care if they have fun. I like to target specific achievements in Europa Universalis IV, some tries are taking 30h+ but I can understand why some people wouldn't do that.
But the main point is still here: if a specific game has a very narrow target audience, where is the problem? To be honest, I get it: random player A doesn't have enough time/motivation/skill/willpower/etc to play a specific game, while many people are liking that specific game. So he wants an easy mode, i.e. several changes in the game to suit him, without even noticing that the game could be less popular for the current players. He could play another games instead, but no.
This is exactly the case with Sekiro. A part of the hype around the game is the difficulty (or in a simRacing game, an ultra-realistic setting). By asking for an easy mode (or in a simRacing game, a less realistic setting) you are asking for a change in the core of the game. This is getting boring, again there are enough games. They could just stop to be selfish and claim "every game should be for me".
If you look at the amount of Souls-like games that are out there today, compared to when it was simply just Demon Souls, then yes, you could consider it a mini genre of it's own. There's a reason why people, even a storefront like Steam calls and has the tag "souls-like", rather than "crushingly difficult", because that doesn't roll off the tongue, nor sound like a fitting sub genre name.
I know you do not play these games, and neither do I, but it's not hard to see what they are and what's transpired since the first ever Souls game.
There is no problem, but there is also no problem when a dev offers a differing difficulty mode, or when people simply mod one in themselves. Hell, I just posted about the devs behind Dying Light putting in an even easier option, years after the game's release, and that game is known and heavily implied to be a "survival" game, as in you fear for your life during the day and the night, yet they have added an option that does away with that very thing, and it isn't harming anyone in the slightest, because people that want to play things on a harder difficulty can simply choose that option, and those that don't can choose the latter.
Do you understand why we as a species try to make our lives a little easier, or does that not come natural to your line of thought?. Yes, the human race does love a few challenges here and there, but at the same time we also like to make things easier for ourselves, from understanding methods to general science, and obviously to games explaining mechanics and tutorials, that have evolved over time.
The thing is, is that those who do not want said game to be changed to suit others, is that they also want other games to be changed to suit them. We have those same people bickering about games being "watered down", and that they want them to stay stagnant and the same, or made more difficult, to which we end up seeing the excuse "game doesn't need to be for you, but I want it to be for me" being used.
What's getting boring, is watching a minority whine about how they want games to suit their tastes over others, but claiming they aren't harming anyone themselves. It'd be less insulting if they weren't so self aware of their obnoxious elitist bs.