The Democratic Party isn't meaningfully a membership organization at any level (The DCCC calls House Reps its members, not you).
Most people don't want to do more than that, of course, and that's fine. Some people do, and many more want to feel like they could.
A triumph of the Obama campaign was that it gave a lot of people the illusion of involvement, which provided a sense of being involved.
And then they shut it down.
I probably do a version of this post every election cycle, at least, but after election day all organization is shut down, and then they try to crank it back up again the Labor Day before the next election.
This is not the best way to do things.