I wonder why people haven’t made a stand-alone game using the creation kit. I assume it’s not allowed in the ToS. But aside from that there would be nothing stopping you from creating a game from scratch with your own data files, right?
Check out The Forgotten City. The original version was a Skyrim mod, but was remade as a commercial game in Unreal Engine. The author prototyped with multiple engines and found Unreal was the most productive for them.