TikTok is about you, the audience. The people posting in TikTok are creators. It doesn't matter if my post is not funny or clumsy or taken with a bad camera. It doesn't matter that I'm ugly. It's about me participating with you. You can interact with my video side by side.
There's a lot of dance stuff but the dancing is just the easy entry. There's cooking videos, science experiments, confessions, inspirational videos, camera tips, art, pranks, and so on.
Their best competitor is YouTube, which does well, but feels a little elitist and doesn't have the little microinteractions. TikTok has mastered 30 second stories. The other social media had recognized that people want brief stories (and even call the feature stories) but they haven't really capitalized on it.