Your world-primer should never be more than a page and it should only contain key details to help them make characters and their backstory.

A really good example of this is Arcanum Worlds' games "Odyssey of the Dragonlords" and "Raiders of the Serpent Sea". The pages and pages of lore are for the DM to bleed into the world's during play. the 1 page primer comprised of a few headers is the perfect amount to create a foundation.

I don't particularly agree with the player = viewer analogy as the levels of agency are completely different. But the point of world building techniques used in narrative is very relevant.

Tldr: short primers are key to good characters, good storytelling is key to good worldbuilding.