What system? What do you use in D&D to determine how a thieves' guild performs when the PCs don't seek to stop them and instead skip town for a while?
Also, why can't the GM of such a game decide that another city faction or visiting adventuring party deals with the guild? Now they're heralded as the heroes of the city and when the PCs return, that's how the world has lived and breathed while they were gone?
There's no way to remove all GM judgment from the process, and I wouldn't want to. But having it be nothing but GM judgment seems to me a very different thing than using a randomizer of some sort. Hence why the "living, breathing world" phrase isn't very useful.
And don't get me wrong... there's absolutely nothing wrong with "the GM decides what happens". I just think we should be honest about it, and differentiate it from other methods.