It isn't just a question of faith. It is also a question of worship.
Yes there are entities that embody those concepts you speak of, but they are not abstract, because people don't just believe in "death" or "life". They know death and life exist. But they believe that they have a name, they have a personality, or that concepts such as "chaos" or "creation" are ruled by entities, persons, beasts. And it is this belief that manifests the gods.
People don't "believe" in destruction or order generally speaking. They know it exists, but this has nothing to do with any religion.
Again : the Old Gods are born from religion, mythologies and folklore. They don't just randomly exist like that.