It’s not just hard games. Old 64 and atari games are hard. But that’s just artificial difficulty really.
Let me make an example of the game im very busy with and you mentioned; dark souls
Dark souls starts hard. You will think things are cheap. But there is no 100% failure rate. With enough skill you can do anything, it is not artificial difficulty.
At level one I beat the final boss; I’ve done speed runs etc
Everything can either be blocked, dodged with good timing, or if you have good timing and reflexes, parried.
Hunter island, there’s a 0% chance to beat the game at level 1, where even final fantasy you can beat final bosses at level 1 sometimes
The skill ceiling for say dark souls is infinite practically
And it rewards skill more than levels, or time spent, or gear. Even though those do definitely count a lot.
The lore in say hunter island is differently presented; very straightforward with not much room.
The lore in dark souls is contemplated, read through items descriptions, seen through cutscenes, implied through dialogue, through exploration. It has a story, and you can make it the direction you want.
I understand it’s very odd to compare something like hunter island to dark souls, but it is what it is, what I define as a “hardcore” game, to hunter island and IOS apps themselves.