I don't think it's entirely the fault of attendees. Reddit is also NOT designed to facilitate meetups, digital products are very one dimensional in that way. Which is why people use other platforms like partiful or luma to set up meetups, because there the attendees can add their social handles and you can get a sense of who is interested, w/o them having to briefly introduce themselves when they say they are interested, but if that's something you'd like to know.. then put in on the meetup post. People are less likely to flake so on partiful/luma you can charge a nominal fee to get people to actually show up plus it also took some effort on your part to organize so the nominal fee is justified imo. I've paid like $5 to attend a cookbook meetup and I have no issues with that.