Development of Hero Formula over Time

I think that the basic structure of the heroic journey has stayed the same since Perceval because it works. Those types of stories are the ones that people enjoy, and have enjoyed for 1,000 years. Why should movie writers and book authors change something that works. Sure, there are a few minor tweaks to the formula but nothing to major, usually. The changes are most often superficial like adding more explosions or fight scenes. But sometimes, the changes drastically affect some part of the formula, usually the ending. A really good example of a hero from a modern story is Neo from the Matrix. He has to learn everything in the beginning, has a romance with the girl, I forgot her name, he has two mentors, Morpheus and the oracle lady and he also has many challenges. The main change is that everything is not happily ever after for Neo. It is for the human city, but Neo dies. I think that is right, but even if it isn't right, the other drastic change is his girlfriend dies. So the story mainly follows the formual for a hero story, but hollywood added some changes to make it more entertaining.