Hussar
Legend
Certainly if creating own world, it would take a lot of time, albeit the campaigns themselves may help flesh it out.
That is why I relied on forgotten realms when doing sandbox, as most of work was done for me and i could just reference the many 3rd edition supplements they had filled out to flesh out things whatever direction the players chose.
Ironsworn does sound interesting though for creating own view of it as such. Are there any quickstart rules or the like to get a feel for the system?

Tomkin Press - The Ironsworn Family of Tabletop Roleplaying Games
Tabletop roleplaying games of perilous quests for solo, co-op, and guided play. Award-winning games by Shawn Tomkin include Ironsworn, Ironsworn: Delve, Ironsworn: Starforged, and Sundered Isles.
It's free and honestly, the rules are so short it doesn't really need quickstart rules. I do highly recommend it. But, to be perfectly fair, my other group bounced off it hard. They wanted more traditional style gaming where they play twenty questions with the DM in order to learn about the setting. If that's what your group is into, they likely won't like Ironsworn.