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.
Agreed, NWN being marketed as an adventure-building platform is why the developers were more engaged with the mod community. Larian are not really producing their games with adventure-building in mind, so even with tools available, the engagement isn't particularly strong.
As games/engines become ever more complex, I think you need a much stronger emphasis on mod-building credentials to get much traction. Even Bioware no longer have that focus, hence the rather limited mod availability with DragonAge after switching engine, which is a shame.