Where everyone can tell their folktales, folksongs and discuss about them. I have in mind an open discussion about our cultures' ancient myths and legends from different people on Earth. I myself am an enthusiast about these topics.
Personally, no. I would not join a community about something like that. While those topics can be intriguing, it's just not my cup of tea. That said, don't be discouraged. I'm sure that there are a lot of people who would find something like this interesting and different. It's an original idea and it could definitely work.
I am interested in those topics, but not enough to join. Unfortunately, that niche is quite small and I think it may be hard for you to build a website around it. Best of luck with it though!
My one recommendation would be to expand your future forum's topic to include other beliefs, ancient history and more. If you expand it so that it's not just about folk stories and tales, I think you may have a chance.