I think the same could be said for headlines. Or TV scripts. Or even layouts and social media ideas. It's not just about writing. It's about going to work and excavating the thing and see what's there. You can't just assume that because you stumbled upon a bone there's a whole colony of plesiosaurs just below the surface.
Using the fossil metaphor, here's how I see a lot of students and junior teams presenting their ideas:
JUNIOR TEAM: We've found this dinosaur bone sticking out of the ground over there. It looks like it could be a cool dinosaur. But we'd also like to run around and look for more dinosaur bones.
CREATIVE DIRECTOR: Have you excavated the one you found?
JUNIOR TEAM: No. But we imagine there could be a whole skeleton underneath. It could be really cool.
CREATIVE DIRECTOR: Well, why don't you try excavating that dinosaur, since you've at least got a bone there.
JUNIOR TEAM: Okay. But we'd also like to run around looking for more bones.
Two skills that will make you a stronger creative are the ability to recognize a potentially great idea, and the ability to develop it to the point where you can prove that it's a great idea.
Speculation and hope only get you so far.