Skyrim's vanilla textures are 2011-era, and the first thing you notice is the blur. Skyrim 202X by Pfuscher is the gold standard for a full visual overhaul, SMIM fixes the blocky meshes, and Lux or Enhanced Lights and FX gives interiors real lighting. These are the texture and mesh mods that make the game look like it shipped this decade — pick one texture pack, then layer the rest.
Ranked by hand, not auto-generated. Every mod links to its full page with install guide + compatibility.