The part I want them to change the most is the lighting... or the colors in general. Once you use shaders, you can really see the game has a "mud filter" as I call it... a greenish brown color filter that is present in any scene. If they made the colors more saturated and balanced it would make the game look so much better! I think that's the one thing that makes the game look outdated. They have this fancy PS5 version, but even on it the game doesn't look that great. I think the game looks absolutely beautiful. With shaders.

Higher resolution textures would be amazing also, but I think removing the mud filter and making the colors / lighting more saturated and colorful would make the game look way better for everyone than if they just increased the texture resolution!