Maybe we can agree to disagree because I don't think a specific demographic is enough to overcome the negative network effect at the start. The problem, imo, is that the attrition rate of dating apps is really high and dating apps are only good if a lot of people are located geographically nearby. You either need broad appeal to avoid running out of people early on or a demographic that is unusually geographically concentrated and usurps the attrition rate (ENM comes to mind for the latter).

Of course, you could always make something for dating without the geo proximity, but I think most people won't want to use something like that at all.

The beauty of new FOSS projects is that they're quite often hosted and developed for free, so I don't think that's much of a limiting factor as long as the community is there. That's also why I think it's important to make it big quickly, because that's the way to get a big enough community before the creator loses interest.