Totally agree. You need a skillful DM and experienced players who want an "open world" for the setting to really work. There is a lot of give-and-take between the players and DM to get the most out of it, mostly to make up rules as novel situations come up. It absolutely falls apart when you have min-max types who want to exploit the systems rather than roleplay them, or players that have a hard time moving outside the DM's storyline.