I honestly don't get the appeal and cult-like following around them.
Dark Souls came out in 2011, right when Youtube started heavily promoting gameplay videos (Minecraft came out the same year). It was probably the only "hardcore" action-adventure game available in consoles, so it picked up a niche.
The basic formula is nothing special really: take any action-adventure game, give regular enemy mobs 5x the HP, 20X for bosses. Crank up enemy damage so that player dies in 3 hits, 4 tops. Boom, you've got a Souls game.
Lots of mechanics are very out of place for a modern game. Enemies just follow their very limited waypoints until you get into their aggro range, then chase using what is very outdated pathfinding: they won't climb trees or get to you if they're not in almost a straight line of sight. Often they'll stay in a walking animation as soon as finding an obstacle. Ladders seem to be an exepetion, though.
Combat AI is very old-timey too. Enemies have 2, 3 animations that they alternate. And they are very rigid: they'll perform their fixed animations through obstacles -clipping through-, like columns or trees, trying to get to the player in a straight line of sight.
I don't think it's fair to call it an open "world" either. A world almost entirely populated by barebone AIs that exist solely to patrol their 2 waypoint routes waiting to attack the player and respawn after resting at a checkpoint makes sense as a "world". Reminds of early 2000s MMOs, specially Lineage II.
Only the player character is actually doing stuff. Everything else just sits and waits.
It's like the game doesn't even pretend not to be a game. In that I think it's somwhere in the oposite of something like Assasin's Creed that tries to explain its videogameness away, where the assasin gameplay is explained as what happens when your character relieves their ancestor's memories.
But the Soulsbourne games scatch a particular itch...
the general sin of melee action games is how unchallenging the combat is. Most of the time feels like swinging a weightless sword with a baseball bat animation much too fast. Or shooting arrows with a bow will be like a machine gun for toothpicks. Show the game to the non-initiated and the first thing they'll mention is how it takes a long time to attack. Also one of the first games with shield mechanics. RPG games before basically slaped a +25% defence! and called it a day.