Our ideas and our premises sound good to us in the same way that a child’s refrigerator art seems good to a parent. Usually our ideas and premises seem as appealing to us as the ideas / premises of the good stories we’ve read. But, as you suggest, the reason someone else’s ideas seem good to us is because of their successful execution. Without any execution, our ideas / premises / outlines probably won’t appeal to our target audience. Even then — even if our execution is acceptable — the ideas / premises / finished stories may not appeal to our target audience. We’re still likely to overestimate the power of our story for another person. This is why an objective opinion can help.

I just watched the original (Gary Cooper) Mr. Deeds Goes to Town back to back with the (Adam Sandler) remake Mr. Deeds. The ideas / premises are pretty similar. But the two movies couldn’t be more different in terms of their audience impact.