A story doesn’t need 9,000 fully fleshed out characters. It doesn’t need 666 detailed settlements with 42 capitals spread across 7 kingdoms. It needs what it needs and not a single line more. Overdevelopment just gets in the way of good flow. That is not to say that rich background isn’t essential to a good story.
I’m a huge proponent of the “developed as needed” approach. Start with the essentials. A mapped city, a couple NPCs, and a few adventure opportunities. Go from there. Add sites when needed. Add culture as a few lines of commentary here and there. Create factions on the go. The machine can do the heavy lifting for you. You just be mindful of your players.