Actually, Craig, I think our parties are as democratic as they need to be. Anybody can vote in his party's primary and have that basic influence. And, if they want to put themselves into the process with greater zeal, they can be activists and get appointed to super-delegate status. Doesn't make you a big shot, but acknowledges your willingness to work a little harder for the cause with some minor perks. And, if you want to do nothing, or have no interest, you can do that too. I am adamantly opposed to insisting on input from the uninformed and indifferent.
The other model you sometime hear imagined is one national primary on one day, with every adult required to vote. In the online world, this is even feasible. But it subjects the project to a great deal of accidental volatility.....and group's like ISIS, which specialize in manufacturing momentary uproar, would put prodigious effort into timing the public opinion snapshot.