Whenever a game gets remastered or upgraded, it's not always immediately obvious what makes the new version so much better. While a couple side-by-side screenshot comparisons can show surface level improvements in lighting and textures, more nuanced improvements can usually take a while to pick out.
That's especially true for a game as massive as Skyrim. Like any other game that came out five years ago, it's easy to forget just what the limitations were back then that a new Special Edition can improve on. Fortunately, the Skyrim mod YouTube channel known as Brodual has put together a quick video to showcase some of the new version's easier to miss changes.
The improvements discussed above include things like the addition of rain occlusion which makes it so that participation doesn't clip through roofs or other in-game structures, as well as improved stability overall that prevents the game from crashing if, say, there are hundreds of NPCs onscreen killing each other all at once.
One of the more interesting changes involves how realistically the water flows. In the original Skyrim, water flowed in one direction at a constant speed no matter what. In the new version, rivers bend around turns and the water flow changes speed depending on the topography.
How water flows in the original Skyrim.
Water flowing in the special edition version. It's one of those things you'd don't realise you care about until it's finally there, helping the game to feel more realistic on a very instinctual level. Of course don't think this means the new edition isn't filled with classic Skyrim nonsense, because it definitely still is.