About the DDF specifically: I'm sure that went the way of the Dodo because Frontier (correctly) had the epiphany that allowing a group of people with no other qualifications other than a significantly lighter wallet weigh in on important design decisions for the game is a monumentally bad idea. All the DDF would accomplish is the establishment of an echo-chamber comprised of the most diehard fans of the Elite concept, and that is absolutely not an ideal environment for good ideas to flourish.
My view is that the DDF consisted mainly of people that:
A - Had played the original games, and understood what made them a compelling experience (which is why they backed the KS in the first place).
B - Of that group, had more disposible income than the average persion.
If you had been able to read the actual discussions that took place (as opposed to just the revised proposals), then you would have seen them go something like this:
1 - FD post a set of detailed mechanics for a particular aspect of the game.
2 - The DDF discuss these proposals, and in general DO NOT suggest alternatives, but point out the flaws in the original proposals, and suggest ways to mitigate these flaws.
3 - FD read the discussion, and occasionally post during the discussion to clarify points in the original proposals.
4 - FD then revise the proposals to incorporate (where FD think it's appropriate) the things that came up during the discussion.
At no time did the DDF determine how things would be, and did not want any ingame advantages.
The DDF (as far as I can tell) fully understood that games today can be so much more than they could when the original games were produced (many have never stopped being gamers), and that the 'Elite concept' can be expanded to incorporate the possibilities of today, whilst adhering to the spirit of the original games.