The thing about the DDF is, they (we, because I include myself) were talking about a different game for the entire duration.While the DDF was 'aspirational' and had caveats, there is still a lot of gold in there that needs implementing.
Been thinking of making a post on that, DDF design topics still not released or explicitly canned.
That game could be played offline.
So, the usefulness or otherwise of the ideas put forward have to be seen under that prism... because it informed every single response that people made to everything that FDev proposed. They decided they couldn't make an offline Elite, and the DDF game (which would have been awesome) comes under the same category unfortunately.