Just a thought:
If character choices (Playbook moves in PbtA games, Aspects in Fate, etc.) are signals from the player to the GM about the kind of content they want to see , stats and moves (especially the basic and MC moves) are signals from the designer to the MC for the kind of content they had in mind for the game.
When a player makes a choice about their character in terms of abilities, characteristics, instincts, and the like, it should send a clear message to the GM saying, “I want to use this in this game, please work with me to make that happen.” Otherwise, why make those choices, if they go unanswered? (This is an important point in and of itself.)
Likewise, MCs can look to the stats and moves (again, especially the basic moves) as clear choices the designer has made to indicate the sorts of situations they had in mind that the characters would find themselves in, and more specifically, the significant parts of the situations, those that they want in the spotlight and incorporating the dice to help decide what happens in the fiction. Not that MCs should be pre-planning storylines, mind you, but instead looking to the stats and moves and seeing if they get excited by the inherent stories set up by those elements.
Furthermore, the MC moves count here, too! They’re just as important a signpost for suggested content as player moves and the Agenda, Principles, and “Always Say”s, e.g. when there’s not an explicit player move for harm against another, look to the MC moves for guidance on adjudicating violent situations.
So, whether you’re designing, running, or playing a PtbA game and you’re coming up short, look to the stats and moves, not as prompts for circumventing the fiction (“I Go Aggro.” “Roll to hit.” “11!” “Okay, you deal two harm. Next?”), but as indications of fictional elements that are supported mechanically, and are therefore charged with risk and reward.
I may be wrong (or it may be obvious), but this is how it appears to me. Thoughts?