But many of the changes Jackson made were, explicitly, because it was made for the World we lived in in the early days of the 3rd millennium. The reworking of Eowyn's character and the introduction of Arwen as a substantial on-screen character were both done because they felt that the story didn't have enough female characters for a modern audience.
Adaptions are always made for the modern world, because ones that aren't fail to appeal to, you know, the modern audiences that they need to watch them.