"Procedural generation is a wonderful breath of fresh air, blowing away a lot of stale thinking and stale storytelling in the games industry. To be honest, it freaks the crap out of many a writer. Why? Because it's impossible to rely on tried and true structures like "3 Acts" and "The Hero's Journey" when anything could happen in the game at any time. Suddenly, the player isn't just going along for the ride on a nice, smooth character arc. This isn't Booker DeWitt coming to terms with his past. This isn't Joel and Ellie building a relationship only to have the hostile world threaten to tear it apart.
With procedural generation, the game is reacting to what the player does, not what the character is expected to do.
The Player = Protagonist
The Game = Antagonist
The Story = What happens as the Protag struggles to overcome the Antag.
There's no predictable plot here, because the Protag can succeed or fail in a myriad of ways. Plot is replaced by Story Experience.
But how do you 'write' for something like that?
For a start, you switch off all the lights in your plot brain except for that one desk lamp at the workstation called Department of Cause and Effect. And then you get down to the business of writing tiny scripts, sometimes just one line, that capture specific moments of cause and effect in your game."