LoD’s aren’t then end all be all to optimizing meshes, nor is using Nanite. You can still go through and reduce tris/verts where they aren’t needed. Some meshes shouldn’t even be used with nanite. It can be the case that they are better suited for LoD’s.
There’s also material clean up, reducing shader instructions and complexity where possible., Texture packing, atlases etc.
Reducing texture sizes where applicable can be extremely beneficial to load/unload times. Reducing draw calls, will increase FPS and general performance.
You should really take a look at this thread.
Nanite has a fairly specific use case. In almost all situations you are better off using traditional methods (LoD’s etc).
Nanite is not a performance magic wand.