I'll be 100% honest. IMHO the reason it was able to work out so well, is because most of the people there met each other previously and knew each other. I don't think I'd go to a random shabbos DO with someone I literally met online and have no clue who they are.
So if you've never been to a DO and have no clue who anyone else is, don't expect to be invited to a shabbos DO. How should I know that I can trust your karshrus? DDF has the benefits of having people from all spectrums and everyone has their own opinion regarding kashrus.
I think this should be obvious, and not just because of the food. A shabbos isn't a DO. Most people would be game to go to a restaurant to meet new people without putting too much thought into it. If you like it, you stay; if not, you walk out politely, with nobody thinking twice. A shabbos is a much bigger commitment, and requires a higher comfort level. I would think most people would rather not spend shabbos with a bunch of strangers. Additionally, if you're spending shabbos with your friends, you'd rather not have a bunch of strangers getting in the way. Of course, if one of your friends knows somebody and says he would be compatible, he'd be welcomed, but the core group would be a bunch of friends, i would think. Forget about the food and the kashrus; do you want to have a joint meal with a bunch of people you don't know from a hole in the wall? A DO is a great non committal way to meet strangers; a shabbos not run by a central program, maybe not so much. The problem is that everyone wants to be that fly on the wall that gets in on the sooper seekrets. A low level shabbos may not generate so much interest, but when people hear about a bunch of "names" that were involved, they get upset that they didn't have a chance to join. My opinion? Get together a couple of your personal friends from DDF (anybody expecting to go to a ddf shabbaton must have a couple of those), and once you have a core group, invite people that you think would be interested and compatible based on what you know about them. It'll get a lot further than being a silent guy on a friendly WhatsApp group, that is the first to pipe up when someone suggests a get together. Just my $.02. (I have yet to hit up a DO, so I'm not really one to talk, but this same scenario and dynamics manifests itself in so many places.)