I've been there. There's been a few stories that I haven't been able to get off the ground because they come out too foggy mentally and every decision I've made to outline them felt like a chore. I think I was drawing from a creative dry well which is why I stalled out writing both stories on the first pages. But everything is a decision whether it comes naturally or forced. I think the difference though is that by forcing you're relying on creative scraps - stereotypes, clichés, worn out tropes. Naturally is when you have something that perfectly fits your story. Take the two stories I'm working on now. One I've got close to 100,000 words, the other I've got 30,000 words. Both ideas I came up with spur of the moment - one triggered by a picture, the other I'm not sure. I just visualized things and started writing. My WIP Falling Child Star I'm pretty conscious of the decisions I've made for the character and the story. In order to make him unusual I made him a dumpster diver - partly the idea was already there because I'd been looking at upcycle ideas for my other WIP In the Pit. I didn't have to strain my brain because I'd taken in something creatively and could draw from it. But my other stalled stories ... I feel like I haven't lived or experienced something or even just taken notice of something yet that will bring them to life. When I do I'll know it.
I've sat down and typed for weeks at a time, finally wrote 'THE END' and called that a story. But going back to read it over later, I've always found that my inspiration didn't shape itself as a gripping tale. Sure, it was a story, but a gripping tale? That's when I pull out pencils and recipe cards or markers and whiteboard and come up with a plan to shape the mess (story) into a gripping tale. I go for walks to let my mind wander so I can find new ideas. I make decisions about whether or not to include those ideas in the final gripping tale. Insights most often come when I'm not even thinking about the story/tale. And in the end, without all these things—the walks, the rough pantser draft, the input of beta readers, the ideas, insights and decisions—I don't think I can come up with a gripping tale. Stories, maybe, but not gripping tales. Of course, whether or not they are gripping tales, I won't know for a while yet. But that's what I aim for.