Ovinomancer
No flips for you!
I violently disagree with this claim. The kind of responses a GM is expected to make in Story Now games are often confused with trying to ad lib in a D&D game, where the scope is wide open and there are few to no constraints. The GM's job in story now games is much more tightly constrained by immediate play and they always have the ability to ask questions as use the answers. The job is not as hard as it's imagined to be. I was stunned at how much easier it is to run a Blades in the Dark game than is was to do even a partial ad libbing in my 5e games. It's very much different.Actually, if the GM can make the answer interesting and useful--and relevant to the question asked--the GM can make the answer anything they want. The only reason it seems constrained is that improvising such an answer is hard and most GMs don't have the bandwidth to do so.
That isn't to say it's for everyone, I just disagree with the breadth of your claim here.