> Yet for every AAA development house that can't prioritize making public versions of their in house development tools, there are games like Minecraft that are almost nothing but modding tools pretending to be games, and getting all sorts of interesting fans doing interesting things.

Minecraft doesn't have any significant modding support from the developer. Official 'mods' are mostly limited to textures / shaders. The real modding tools that exist for Minecraft were created by the community and largely exist because Java is comparatively easy to reverse engineer in addition to some 'off the record' style support of the mod lib authors by the game developers. The whole mod scene has gone through various phases of questionable legality and unknown future. The Minecraft mod scene exists largely in spite of the game developer, not due to it.