Or in other words, is the plot/story more important than how it is executed?
I'll use as an example a fantasy I'm writing. If I boil it down in a few words, it would be "a kinda-typical-but-different medieval save-the-world fantasy done right".
The "but different" and "done right" are the best part of it and what makes me proud of this work. It's the "how", the execution, how it's done, how things work, the subversions, etc. Although it's nothing groundbreakingly innovative or spectacularly amazing, it's just pretty interesting and well made.
But the real problem is the other part, the "kinda typical medieval save-the-world fantasy", i.e. the "what". Although the "how" is pretty interesting, I cannot see the "what" in this story the same way, since I kind of grew tired of this type of story because of how much it is repeated ad nauseam in other works, so the "what" ends up obfuscating the "how"'s shine. I don't want my story to be considered "a typical fantasy done right", but instead, a good work on it's own.
If I change the "what" I would have to discard pages and more pages of "how", good content that depends heavily on the "what" (it's ~50% complete, ~45,000 words, two years).
So is it me or is the "what" more important than the "how"? How to make the "how" overcome the "what" and prevent the shine of the execution from being obfuscated by the simple premise? How to achieve that without changing too much what has already been setup?
I know that a good premise badly executed is bad and a simple premise well executed is good, but the problem is that I think the execution of my story, although very good, doesn't have enough "weight" to be interesting/attractive on its own. I think if I improve the premise, it will have a bigger overall value. A good premise and good execution is always better than just a "more of the same" premise with good execution. So there's two possibilities: to improve the premise and discard loads of content, or to improve the execution to be so good that the premise doesn't even matter. I fear to say that both are inviable: the first is a waste of done work and the second is beyond my current capability.