Since, you always have to do a Move, in order to roll dice, there often is a "Catch-All" move
Personally, I think it's bad design to have "catch-all" moves in PbtA games. When people have an instinctive "it feels like we should be rolling dice here, which move should we use?" reaction I think it's just fine for the answer to be "actually, we don't roll dice for that in this game". Not everything has to be a mechanized move. Sometimes you'll just say what your character does and it won't map to something you roll dice for as a player, the GM will just say what happens in the world as a result (often you'll trigger the "look at the GM expectantly" prompt for the GM to start using moves from their side). What is or isn't a mechanized move is part of shaping the lens through which a player experiences the situation in a PbtA game. To my mind, "catch-all" style thinking is closer an "I'll just say stuff and let somebody else think about the mechanics" style of play.
The GM having complete choice of what exactly happens on a 6- (instead of taking damage while fighting a Troll, the GM might say: "The Troll takes your puny sword and throws it far away") means that death, unless it actually fits the story well, is out of the question in PbtA.
This may be a question of semantics, but I think that death might "fit the story" any time you're fighting a dangerous opponent. I think there's a "say what honesty demands" element that ought to keep GMs from using their move selection to "save" players who really are in a position to potentially get killed. I remember listening to an AP of Apocalypse World from The JankCast podast where an NPC had a gun to a PC's head (or something similarly threatening), the PC tried some psychic manipulation and got a 6- roll, the GM tried to have the NPC get all flustered and just graze the PC with a gunshot, but the player felt that was really cheesy, that their character dying was the only reasonable resolution to the interaction.
Actively solving problems is not really being rewarded, but a necessity to play the game;
I think there is some rewarding going on in the game, but it can be a bit subtle. If people are playing their characters passively or reactively it probably means they're going to be doing a lot of "looking at the GM expectantly". Which means the GM will be making GM moves, which are probably going to make the character's situation worse. But if the character is proactive they're probably going to be making a lot of player-faced moves, which are often successful at getting them what they're going after. They become the agents of activity in the story, and consequences of their actions will tend to spin off and affect what other characters are doing, keeping the whole situation dynamic and ever-evolving.
Yes! … but my summary had to end somewhere.
Catch-All Move is very much meant in a "There is no move, but there definitely is a risk (as per the fictional requirement of Act under fire e.g.)-Move" way. To do it, do it, don't roll dice to walk to the other side of the room, or to see if you spot something by pure chance – which is somewhat what I meant with "Please roll a dice, because reasons" does not work in PbtA.
Which is one of the core things in practice of PbtA:
Saying what you want to do, and asking the GM whether what you think you should roll actually applies.
As you said, in PbtA GMs should not be afraid of saying things like: "This NPC has no chance of defending, you just deal your damage, and kill them; no roll required".
Which definitely is a case, imo, where death fits the fiction well. As you mentioned: Say what honesty demands, but also letting everything flow from the fiction and making the world seem real.
The "death fitting the story" thing was obviously meant as a "jab" at DnD in regards to my recent blog-entry about fudging dice rolls. 3 goblins against a Level 4 DnD party should not be a threat, story-wise, but if the dice think that goblins should only roll 18+ and players only 3- for an hour …
Death was basically out of the question, but DnD is no story game. In DnD the players might die horribly, while in Dungeon World … The players might also die if the dice really tell a "the PCs die to measly goblins now" story (and we're here to play to find out what happens, if this is what happens: okay?!), but the GM has way more ways to spin it towards not death, than in DnD.
Not that the GM should bend reality for it – In Dungeon World you can still do a
"The Dragon is about to kill you, and then … he flies off, because reasons!"
"Ah, okay, the GM doesn't want to kill us, everyone ¬_¬"
just like in DnD, of course.
This is a very good way of phrasing what I wanted to say, but failed at, with my "Players will eventually reach their goals, and are thus encouraged to pursue them." – even their active pursuit is being rewarded.