the story of LOST is, first and foremost, about the survivors of Oceanic Flight 815. I want to see what happens to them.
See, this is what I don't get about these characters-only claims. Essentially these characters and what they do is now tied into the mythology, so the rest of the mythology becomes important by extension.
For example, Saving Private Ryan takes place during WW2, but you don't need to know about anything beyond Normandy, who the enemy is, and what their mission is. But the reason for that is because the mythology is already a given. In the case of a complete unknown, more elaboration may be required for most who are unfamiliar with its workings (or can't just look it up). Combine that with the show presenting itself as mythology driven and it's clear that there needs to be a balanced focus on both. Where that balance lies becomes the most difficult part to achieve.