Counter-point: there are always unassailable forces in Dark Souls. Giant immortal trees, Gods who disguise their siblings corpses and paint you as a murderer if you try to do anything about it, the fading light of the age of fire, actual countless giant "amygdala" creatures bigger than the one you get to fight in Bloodborne.

There is always this sense that no matter how much you fight, nothing really changes. It's just a slightly less populated ruin.

Darkest dungeon does it well. Nothing is unbeatable, but the odds are stacked against you and the stress mechanic snowballs things pretty hard.

Last dungeon I ran, I had to decide whether to try to save an irrational team member and risk stressing everyone else out, or let him die of a heart attack to salvage the others.

Leads to a lot of "This is insane, I shouldn't be here" moments.

It's an interesting thought but you gotta admit it would be silly to have a boss in a game that you absolutely cannot beat. Like your character just gives in to madness/despair as soon as you encounter the boss.

Now maybe if you had a dark souls boss fight while a different big unimaginable entity tries to catch up with you might be interesting. But that also might just be a countdown timer on the boss fight which could be lame if not done well.