a tip i frequently find myself telling home GMs/MCs about tabletop games: do not design a setting with the same level of thoroughness as you see in an existing ttrpg book. we have to do that as ttrpg authors because we are trying to provide lots of interesting hooks for lots of different potential adventures at lots of different tables. you are hanging out with four or five other people. your setting only needs to interest y'all. don't make 60 factions when 6 will do
In addition to interesting hooks, we are also creating examples of what the game can do. They help set the tone, give options for GMs who need to fill in a blank, and show some of the things that are possible.
As Kavi said, most tables don't need EVERYTHING in the provided setting and should only use what is most relevant to them.