Not really unfair; with the NWN games, people were actively creating content well ahead of the game releases because there was a lot of community engagement by the developers. Obviously the quality and usability of a toolset, post-release, also affects how many people can indulge their creativity, but you have to spark some interest early.
Maybe nobody cares as much any more, or perhaps the creative community prefer Bethesda style RPGs to D&D?
You bring up some good points; but NWN was also marketed as a game where you could create your own adventures. It was a selling point of the game. Though DOS2 modding was huge, I'm not of the opinion that mod support was one of its biggest features. I think it just extended the game's staying power.
So to some degree, I think the answer is that the creative community prefers the other styles of game. But more because they're more accessible, rather than what type of RPG the base game is.