[Trasmatta]

> Overly complicated world-building requires mountains of expository prose to expose the complexity.

No it doesn't. The presence of the complex world can surface in subtle ways, without the need for extensive expository prose.

https://en.wikipedia.org/wiki/Impression_of_depth_in_The_Lor...

[jl6]

> Far, far below the deepest delving of the Dwarves, the world is gnawed by nameless things. Even Sauron knows them not. They are older than he. Now I have walked there, but I will bring no report to darken the light of day.

The lack of detail and explanation here does work that no amount of exposition could do.