I have created a highly realistic medieval world. The world in and of it self is alive and things and people will change just like in real live.
I wrote my own style of Players Handbook for a in between of 5e 2014 and Adnd 2e.
The player part is currently around 300 pages including the gods, fully reworked races, some class changes, rules and much more.
This setting has a lot of restrictions towards outworlds classes and races that just don't fit the world.
And just like real live your actions will have consequences. For better or for worse even simple things can lead to big changes in the world which you might or might not be able to experience.
This World doesn't evolve around you. You live in it. And actions have consequences.