That's kinda impossible, though, unless you're new to the game and 5e was your introductory edition.
What this discussion shows is that people don't really do their mental world-building based right off the books. They already know how a D&D setting
should work, and then it becomes a question of how closely do the books actually match their preferred mental model.
No one in this thread has actually changed their mind about the cosmology of their own settings based on something somebody found in the PHB.