No, a directory doesn't get bigger because it gets more submittals. It gets bigger because its editor does more work. Submittals help you find sites to review -- but THAT part of the job is by far the easiest and simplest! All the real work, and all the hard work, is in reviewing, categorizing, describing, maintaining. If you can do the real work, then the dead-easy part will not be a problem. Even without any submittals at all, any idiot can find more sites in a day than he could review in a year.
Just to put things in perspective: a few of the most active ODP editors add tens of thousands of sites every year. One editor like that will have done over a thousand times as much work on the ODP as you've done on your directory.
Are you willing to spend a thousand times more effort on your directory than you have so far? For the next five years? In addition to earning a living?
If you do that, ... you probably WON'T get added, even then. Even today, that's just not quite good enough, and in five years the competition will be steeper. There may not be enough big directories, but there are way too many little directories -- and so long as people keep doing the "easy parts" (like the submittal scripts) and ignoring the hard parts, then there are going to be way too many little directories without content.
And even if there were more big directories, then the little directories would be even more superfluous than they are now.
The way to get people who care about doing good work is simple.
(0) Find something you (all by yourself) can do better than anyone else has yet done on the web. (For directories, that is rather difficult!)
(1) Have a good reason to do the work. If you want people to help you build your own website, you're going to have to give them a reason. A REAL reason. "Help me get big" is NOT a reason anyone will care about! "Because I'll pay you" is a reason. "Because you can help society more here than you could doing the same thing anywhere else" is another reason. "Because you can betray me, and use the directory to help your own websites" is ... a reason you have to watch out for!
(2) Do lots of good work yourself--better than other people are doing it. (here, that means better than the ODP and Yahoo!)
That's the way big sites get started. A big community site begins with a big personal site. If you want people to help you put books online, you'll have to do the first hundred or so books yourself. If you want people to help you collect links, you'll have to collect the first few hundred thousand links yourself.
(3) Provide a really good user interface for the helpers. People can volunteer at all kinds of websites -- they aren't going to waste their time cramming information into a site if its server isn't fast or the user interface is clunky. It isn't good enough to make it POSSIBLE to work. You have to make it EASY -- easier for people to do the same thing on their own site, or on other community sites. A good user interface is hard to design, and hard to implement well. If you don't have professional training and years of experience, you will will almost certainly fail here.
These problems may seem insoluble already, but the problem of "getting big" is, of course, much more difficult. I can't suggest a solution. (Fortunately, it's not a problem I have to solve.)
