It’s not that Souls-Likes are hard, it’s just death is a mechanic in them. We traditionally associate a death screen as a loss, in that sense you have to redo a section of a game with no additional reward. But in Souls-Like games, death resets the enemies but you can get your lost experience back on top of the newly acquired one. This means that at some point the section should become trivial because you’re potentially over-leveled. A Souls-Like can kill the player fast because the return to the point oft death is also fast and rewarding.

That’s in my opinion is what makes a Souls-Like a Souls-Like, it’s that gameplay is paced with player death in mind.