This is probably a fundamental design challenge of having a story-driven #rougelike. You either need to end the story at first completion (which demotivates the player from repeating) or continue the story and find a way to progress the mechanics in line with narrative tension.
Clearly the devs went with the second option, but I'm not sure it quite lands the right narrative hook or mechanical change to keep me invested.
I'll probably play at least a few more runs, but I suspect its more due to my desire to better master the game mechanics rather than the narrative.