The DDA was done in much the same way as SOTA (Shroud of the Avatar) 'dev' backers discussion was done.
That is, a placebo. It was a farce perpetrated by the actual developers to meet a Kickstarter line item, and then ignored, discarded, and forgotten.
It's clear that interactive GAME developers are an extreme minority. Requirements gathering, and then iterating on deliverables and new features is, at least for me as a corporate developer, not optional. NOT optional. My clients/customers absolutely insist on this feedback loop being as short as possible, and without insulation. I speak directly with the end-user(s) or with a representative of the end-user(s) that has collected and collated all feedback and RFE's.
Further, once in production, I can make no feature change without it being requested by the user. I don't just get to make crap up and put in features because I feel like it. The only exception to this is security patches/fixes.
Game developers evidently just get to do whatever they feel like and abuse their customers with no accountability. It's insane, and honestly, I don't know how they continue to get away with it.
I think you are painting too bleak a picture. Certainly the DDF has been well and truly abandoned, and the 'God like powers' FD used as a lure to get people to stump up to the DDF level during the kickstarter shows no sign of appearing. But some credit to DBOBE, in that when I pointed that out in an 'Ask me anything' he did not just dodge the bullet, and implied we would get something eventually. Perhaps we might, one day, but I'm not holding my breath.
It is clear that to some extent FD found the DDF useful. They had to go through the detailed design stuff in any case, so publishing those designs to a closed forum that would then argue about them at (great) length was not in and of itself much additional effort. Someone had to monitor those discussions, sure, and that was extra effort, but not I suspect a huge amount. In essence they only made major changes to their design documents when met with almost unanimous disapproval, as they got with the original hyperspace 'rooms in space' approach which got the thumbs down big time, and led to a rethink that got us to supercruise.
However, a time came (and it was ages ago - at least a year ago) when they just stopped. Nothing was said, they just stopped. Some things never went anywhere near the DDF (powerplay for one, and we saw nothing really about the planned expansions, though we went off topic to those from time to time). So I do not think it was a deliberate placebo, certainly not at first. But at some point someone obviously decided that the extra effort to 'look after' the DDF was counter productive, and it was stopped. From where I sit, the mixed (at best) reviews of powerplay, and the work they will have to put in to 'sort it out' (assuming they decide that is important enough), shows that running the ideas against the DDF before spending all those development man days would still have been a good idea.