I don't think that "Most Important" is a label that catches a single, unambiguous thing. "Important" is a big label that we use to say something like, "Is in the class of things deserving my focus and attention."

"Most important" would then seem to be something like "The single item most deserving my focus and attention."

(If there is another definition of Important being used here, that points to Important being an ambiguous term that may need to be better defined.)

But there probably isn't a single item that is always most deserving my focus and attention. If I haven't slept in 3 days, sleep becomes the most important thing for me. If I haven't eaten in 2 days, food becomes the most important thing for me.

I suppose you can try to abstract away the "my" to "the single item most deserving (everyone's?) focus and attention" or create some specialized caveats like "aside from human needs" or something like that, but even then I am not sure that a single item gets the sort of consistent Importance that you are implying. I suppose it is possible that you have found some incredibly clever method, maybe finding a unifying principle under all of the things a person might find important, but I am skeptical.