I think the debate here should be focused on how to successfully support modding in UE4. There are two ways: 1) access to the unreal tools and editor which requires a license, or 2) write your own modding API and content system. Option 2 should be familiar to anyone who has shipped a game using Unity: there is no real way to allow users to mod your game except through custom API’s and asset loaders.
For my project and business we’ve decided that option 1 is fine, but I think people have a valid case for option 2. For my part, I don’t understand exactly why people feel like Unreal should support some mechanism for option 2 as a built-in .
As you said Skyrim has a very active modding community and if you feel like a pay wall for unreal tools is a burden then by all means you should pursue option 2.