It adds a bunch of different stuff that the original engine was lacking, like Distant Terrain, the ability to use textures with actual bump maps, native support for macOS and Linux, and better physics/smarter AI. Since it is made from scratch, it also lacks virtually all of the bugs that the original morrowind engine had. There’s alot of other features too, but the list is too exhaustive to go over in a single post.

Currently modding Morrowind on the OpenMW engine, and getting it ready for a new playthrough :3