If its your first time playing, blind play without any guide or back seating, depend on your preference and your luck, the difficulty could vary between very easy to very hard.
For example, if you don't happen to use magic user and chosen a pure melee, and you somehow manage to miss some of the helpful early game gears (such as flame dragon sword, crescent falcon etc.), and some how you went straight to second stage of a world without knowing you could finish all the first stage first to get better gear. Yeah, the game could be incredibly difficult
For those of people think Demon Souls is easy, from a retrospective view, it is the easiest souls game because of how easily the game is exploitable, and you could became incredibly powerful in early game etc. When talking about difficulty of a game there is this dilemma, once you've beaten a game its impossible to pretend you don't know anything and experience it again like your blind first playthrough. A pure blind play (no guide, no gameplay spoilers, no backseat from friend etc.) its not that common when it comes to souls game, consider these games were likely the hot topic when it was released, some gameplay aspect were spoiled to you without you even realizing.
I remember in 2009, my first blind play, I went straight to Flame Lurker without complete any other world first stage (except 1-1 and 2-1 of course), with starting gears (no upgrade) only, at one time I felt the game was impossible, not because of how hard the boss was, but because of how frustrating to even get there
Same thing happens to me when my first time play Dark Souls as well, I don't know there exist Undead Burg, my first destination after arrived at Firelink Shrine was New Londo, after getting my ass kicked countless times by Ghosts, I gave up and went to Valley of Drakes of course that's not going to went well either, finally I've discovered Catacomb, after getting hours of ass whopping, I've decided this game is enough, thinking what an impossible mess this game was. The next day when I saw other people discussing (Undead Burg), I'm not quite sure we are playing the same game.