A page needs to be already ranked at the top, or at least on the first page of serps for Meta description to start making sense. (Because no one would see it otherwise. :) ). Obviously, other factors influence the page to get there, and it is well known that MD has nothing to do with that. Why would Google read someone's description of the content, when it can read the actual thing and decided for itself. That being said, a lower-ranked results can perform better than a bit higher one, if it has significantly clearer and more catchy MD. MD can prove to be highly valuable for the final stages of the efforts to reach the top position. Indirectly, of course.