There is an essential difference about difficulty in retro games and games of today. It is not as easy as old games are harder.
When you progress in a game enemies becomes tougher, meaner and harder to kill. In today's games you pretty much compensate all that with an avatar that makes the same amount of progress in fire power, skills and health points - which keeps the overall difficulty setting constant through the game.
In older games character progress does not play such large role. Instead you need to learn how enemies works in order to beat them. You cannot trust your avatars strength will save you in times of trouble. Retro games a less forgiving in that sense.
Dark Souls is much more of the old school. Is is not unfairly hard, but you need to learn how to master the controls, master the game in order to beat it. Your progression as a gamer is much more important than your character's progression in the game.
This is why gamers used to hand holding will give up after 15 minutes, meeting the first boss, and retro gamers will recognize the style of the game and become enthusiastic about it.