The GM or DM did a lot more than simply present players options. He or she was the narrator and guide through the game, but had to remain flexible as well.
This, I would agree with, but would argue that the game is really not being very flexible.
Really, most quests are "sit down and listen to the story we are going to tell you" or else you have the option of "don't listen to the story at all". That's basically reducing it to the interactivity of a movie - you either watch the movie, or not. Well, OK, so you do have the "option" to screw up and die, but that's really just brining us down to the interactivity of a Quick Time Event. (Click attack button at dragon to not die!)
To give a more clear example of how the Radiant Story system
should have worked, let's say you want to build a quest around a dungeon that is a crypt with a lich in it. We're always going to use this crypt and lich, because making dungeons is hard work, and so, we want to make sure the player always visits this dungeon so that we can make the most of the resources we invest into the game. However, we also want the player to have choice, and those choices to have meaning to the player. How do we do both?
Well, let's see, if the player is a sneak thief, simply have some of the local rogues mention the treasure of the crypt, and let the player find out there's a lich at the bottom who doesn't like having his house raided the hard way. What if the player is a knight-errant type? Lich kidnaps child to perform profane ritual sacrificing child's life, and the hero is asked to rescue the child. Player some sort of religious templar? Send him/her off to end the profane rituals of the lich. Player a necromancer? Leave hints about how there is a lich who knows of secret arts to increase his/her magical power, and let the player clear the dungeon just to try to negotiate with the lich. Maybe even have a peaceful resolution with the lich, or maybe negotiations break down, and they fight, anyway. Maybe the player is involved in some larger intrigue or another, and the player is told that the lich has some secret, and so you have to find a way to get that secret out of the lich... but will the character be willing to work with someone who has nefarious interests and asks the character to do disturbing things in exchange for the supposed greater good of furthering the cause you are along on?
Here, we get to use the same dungeon and lich, and have pretty much the same dungeon crawl as filler, but the meaning behind the character's actions are all
wildly different. Again, this is the sort of thing you should be able to do if you just use a design philosophy throughout your game like what that "Radiant Story" was supposed to give us. One location has a half dozen different conflicting quests and meanings, depending on what sort of player is going to be thrown at it.