The most thriving mod communities are ones for games that have essentially been abandoned by their publisher. Bethesda is infamous for trying to integrate with its modding scene and personally I don’t care for it.
This is what buying from coop developers is like. You know that everyone involved has agreed that everyone else is essential to the creation of the game and that everyone receives a cut in one way or another.
Writing plain old JavaScript without a library or framework is nice while you’re learning. Too many people will learn a single framework and not have any idea what the underlying APIs are, so the transferable skills are minimal.