Here is the bit I quoted. There's no question in there.
DW and similar games have potentially multiple ways to handle it. It really depends. But any time we try to take something in fiction and then map it to play, there's a possibility it doesn't work 100%. It's rarely a perfect translation.
I'll pose one way. Gandalf's player said "I want to see if I've learned anything about these doors in all my studies". In DW, this would be Spout Lore move. But, Frodo's player says "Hey, can I help him with that? Maybe I know something or can figure something out that helps?" and this would be the Aid action, which depending on the roll, would grant a bonus to Gandalf's roll, but may also put Frodo at risk on a partial hit or a failure.
So Frodo rolls an 8 to Aid, and that gives Gandalf a +1 to his roll. He winds up rolling a 6, but with the +1 that gets him to 7, which means he succeeds, but the GM can make a move.
Given the circumstances... the disturbance in the waters already having been established, and needing to make a move on Gandalf's roll, which also has Frodo at risk, the GM decides to have the thing in the water collapse the doors behind them, leaving them no choice but to press on into Moria (Reveal An Unwelcome Truth) and also to have the creature catch poor old Bill (Use Up Their Resources).
Again, that's one way to deal with it. There are others that we could apply, other ways to interpret it.
Those were some examples from 5e. Though, like initiative, there are plenty of other examples from all other editions of play. Giving D&D a pass for its game constructs, but labeling those of other games as "artificial" or "forced" or what have you seems a bit unfair.
What other ideas do you have in mind? I know of a few games that I've played that have a better system than Hit Points.