Wtf are you talking about, Skyrim has dozens of amazing quest mods, and hundreds of quest mods overall.
It has major gameplay overhauls, it has custom skeletons for animation, it literally has mods that rework the animation system entirely. Modders added a survival system almost a full decade before Bethesda did.
There are mods that add new continents ffs, what’re you talking about? One of the quest mods was so good it literally got turned into its own game.
Edit: There are currently 60k mods for Skyrim Special Edition, and about 70k for the original Skyrim. Meanwhile Morrowind has 11k. Wtf are you talking about??