The power of adventuring through New Plan or seeing the map of the Forgotten Realms for the first time is in the gaps in the maps. The sense of possibility that these give -- not every rumour is true on the rumour table but it could be. And as a player in this space or referee running it or video game designer trying to make it or author trying to write about it, you try where possible to try to smudge the margins -- to spill the writing on the page or pixels on the screen out beyond their constant boundaries to excite the imagination of the participants about a thing that you cannot possibly create.
I have for nine years now been making what is for most people an unplayable game -- Sixty Years in Space -- which has had a modest level of success in part because people reading it fall in love with the idea of the game, rather than its implementation. It works best in this fashion as a science fiction novel without any characters in the genre that is the most successful at telling stories without characters. Sixty Years in Space is the natural conclusion of this process of spilling pixels beyond the boundaries of the page, because it describes a thing that will never exist, empowering hypothetical players to use the roguelike tools of procedural generation, systems expression and permadeath to literally add colour to space.
But you could easily go in another direction with the same roguelike tools. Rather than expanding on absences, you can build a total systemisation engine: a series of interlocking systems that encompasses every possible interaction; procedurally filling in all the gaps on the map; and use permadeath to build an attention field with slopes between boredom and adrenaline. Dwarf Fortress and Caves of Qud both do this: Dwarf Fortress as a city builder/fantasy world simulator and Caves of Qud as an open world RPG. In Caves of Qud, instantiated players consume what looks so far to be well implemented genre fare in a science fantasy wish fulfilment engine. It fixes "no gaps in the map" by ensuring wherever you look there's enough detail to excite you, without any of the friction of it having to make sense.
I don't intend to disparage Caves of Qud, which is more than happy to leave gaps for you to fill in its vast sweep of history, in its dull water-vine filled fields, in the articulation of its visual language and user interface, but more want to highlight that that the roguelike genre is a robust and vast enough an usul to contain both multitudes.