Precisely. Aside from physical disabilities like colorblindness that can cause an unintended disadvantage among people who would otherwise be capable of playing, there's little point to complaining about a game's difficulty if you simply don't have the mindset for it. The point of FromSoft's games, more than ever, is to be hard. Adding an easy mode to such a game may make it more accessible, but it would also likely defeat the purpose of how it was originally designed. There is plenty of room to debate if a game is fair in its difficulty or if there are elements that make the experience harder without adding anything meaningful to the challenge (the health decrease in Dark Souls II), but to say that something is "too hard" is subjective at best and misses the point of the work at worst.
A lot of arguments like this also forget that there are ways to manage difficulty other than different modes. Dark Souls gives you the option to level up, reinforce equipment, summon allies, and kindle bonfires if you find it too difficult to get by a section or boss. Yes, you'll have to grind in some cases, but strictly speaking, attempting that section/boss over and over is also a grind. Plenty of Souls-likes allow you to get an edge in that fashion. Some might think grinding also misses the point, but the devs have purposefully given players the option to do so; those mechanics serve as difficulty adjustment. (It is missing the point if you grind excessively, mind you. If you have trouble with an area, you level up a couple of times, not 40 times; you do it enough until you're able to overcome that challenge.)
It's understandable that Sekiro would spark such sentiment, however, when it offers so little in that regard due to its extremely tight design. If you have trouble with a mini-boss or boss, there's no way to increase your health or your attack power, because that requires you to defeat them in the first place. Aside from prosthetic tools nad a handful of skills for which you can grind, all you can really do is keep trying until you win. It doesn't help that your arsenal is so limited either; Dark Souls had enough equipment variety to suit many playstyles, but with Sekiro, you have to play the parrying rhythm game. I got as far as the final boss and I put the game on indefinite hold because it stopped being fun to overcome the same kind of challenge so many times, even with how well designed I would argue it has been in terms of difficulty. I could beat him eventually, but I don't feel it would be satisfying to do so.