You're confusing me saying I don't find GNS useful with me saying I don't believe there are creative agendas. I'm on the creative agenda train, I'm just not getting off at the GNS station.
There's certainly an interesting discussion to be had about what role the fiction plays in games where players are more invested in displaying tactical skill and in-game knowledge. I'm unsatisfied with the explanation that it exists just as a space to manipulate for advantage. Unreliable currencies (such as are garnered by judgements of the fiction) are unsatisfying for hard-core competitive play.
Hence why I say "Step on Up supporting" texts. If (I genuinely don't know) there are no texts that explicitly support Step on Up play, people could still be playing Step on Up by drifting game rules in play to support their creative agenda.
But that's all about the far less interesting subject.
Here's what I find interesting and useful:
I think there are three broad aspects of play that contribute to creative agenda - three sources of enjoyment that in combination (not exclusively) make up a creative agenda. Here's what I think they are:
When you play a game, you produce fiction, when you look at that fiction, when you "read" it as a text, it has a meaning - a message. It has a theme. Like, if your young farm boy grows up to kill a dragon and marry a princess, it has themes about personal agency, heroism, and so on. If you play unscrupulous mercenaries murdering orcs for pay, it says another thing, about the value of the lives of "other" peoples, and such. Doesn't matter what you intend to say with your game, there's a meaning there. Some groups pay attention to and appreciate that meaning as they're playing. Some do that more than others.
Some groups enjoy play where the meaning is explicit and negotiated during play - you don't know what the meaning of the game will be until you play it, but you care about which way it goes.
Other groups want the theme to be more like an organising principle: a single question we set up at the start and then find out the answer to in play: Can good overcome evil? What price loyalty?
And some other groups want the theme to be a statement that's reinforced through play (they might not say that, but they do). Like "Good always triumphs" or "Other cultures are sub-human" or something like that.Experience
When you play a game, it makes you feel certain things. Like in AW you feel like you've been punched in the gut when you've gotta make some hard call. Or in The Mountain Witch you feel tingly and suspicious when you think about what the other characters' Dark Fates are. Or in Bliss Stage you feel weirdly exposed and intimate the first time you go into the Dream. Some groups care more about the experience of play than others.
Some groups appreciate feeling very close to how their character feels. Play is for feeling strong emotions, for making tough decisions, for seeing how it feels to be in particular circumstances. Good players get close to their character.
Some groups appreciate feeling closer to the other players when they play. Play helps you understand people differently, or helps you reinforce social bonds. Good players are emotionally vulnerable in play (or at least amiable and amicable).Performance
When you play, you're displaying skills: improvisational skills, acting and oratorial skills, tactical skills. Also knowledge of the game's rules, the game's setting, and so on.
Some groups appreciate a well-performed character. You act out a powerful scene, and everyone else finds it convincing and enjoyable. You talk in-character for an hour, and everyone is like *high five*.
Some groups appreciate tactical skill. You moved your dude into the right square, maximising your chances of hitting the monster. Everyone nods, being like "right on". Often those same groups appreciate clever use of in-game knowledge, like, "I took sleep because it's the best spell" or "I brought fire-arrows, to use against those trolls".
Every group will have its own way of appreciating the three things above. Some of them will get a lot of attention, and some of them will get very little. They're all important to the experience of play though.
I think that talking about these three things is useful to explaining play and design.