Wow, thanks for writing such a thorough rundown of the game!
You're right that I designed this to be played as a standalone game. Something a bit shorter that can still create a certain kind of emotional buy-in. But it can work as a part of a larger campaign for all the reasons you outlined.
For both uses, the game hinges on creating those cultural keystones. Those things anchor the festival and give the feeling of a complex culture.
However you use it, I hope you enjoy it!