I have come to agree with this. And I'd like to go a little bit more into "inextricably" and how that might relate to the portability of skill constructs (or parts thereof).
Say we take inextricably as sincerely as we possibly can. So that skilled play really is a matter of agenda (solely) and skill constructs are not portable. I cannot say from outside an agenda that play done by that agenda is or is not skillful. I can only make such a judgement when I am willing to embrace the agenda. So if the agenda were "tell stories" then that determines the skill construct for that context. This is where I imagine
@Ovinomancer might be opposed, because I think he might say that a "tell stories" agenda is one that can't have a skill construct... skill doesn't apply to telling stories.
Alternatively, we can have a notion of portability. Then we seem to be saying that in a skill construct, there will be skill concepts that have meaning only within the context, but there will also be skill concepts that have meaning
across contexts. So now we have said that skill is not inextricably wedded to agenda. I think
@Ovinomancer must think something like this: that skill concepts are portable (including rejecting some concepts as not skillful).
Hence, burningly curious.
Perhaps where we might find a continued bone of contention, is that I see TTRPGs as rather malleable. I don't think the rules hard-force the play. Given I don't think that, I expect that multiple agendas can employ the same game-as-artifact.
I have this thought that games might be best seen as
tools (this is in contrast to other definitions, which are easy enough to find). As with tools, they will be better suited for some things - banging in nails perhaps - but you can always hit someone over the head with one.
I hadn't thought about the rudderlessness like this before. On one hand I agree with it. On the other hand if you have a rudder-audience mismatch then your design won't succeed anyway. Well, it can succeed on its own terms - as a piece of craftsmanship - but not in terms of being very widely embraced and enjoyed.
One can approach design audience-first (this is the usual mode in commercial design) and develop the creative agenda with that audience in mind. Additionally, creative agendas tend to be layered. Many designers have an intuitive or philosophical agenda, and layered on that for a specific design might be a creative agenda. We are oversimplifying when we use the word "agenda," but I imagine you know that.