Dark Souls games should be able to adjust difficulty.

It does, you just have to use stuff in game to make it easier rather than sliders, which are one of the worst ways to adjust difficulty. Using a shield, actually upgrading your weapons, exploring the world, git gud, summons and simply levelling up go a long way. Magic has universally been the easy mode and I'd say str builds entered this in ER too.

ER has by far the most ways of adjusting the difficulty too btw, which shows that they are adding in more easy mode options. 90% of the bosses are straight up skippable, as are half of the areas and several of the legacy dungeons. If you don't want challenging content, you can literally just not do it. You have literally overpowered summons that can solo bosses for you. Some incredibly strong weapons and talismans are in the starting areas if you just explore a tiny bit.

At this point, if someone still wants an easy mode added then they're asking for a game that isn't Souls. It's totally fine of course to want stuff that isn't Souls, but you don't have to take away from the Souls games to do this.