This the problem will almost all of these apps -- even if they offer solid export options, they all handle data so differently that migrating is becoming more and more difficult. Ideally we'll see more standards arrive (like the YAML Frontmatter in Obsidian), but I'm not sure we'll ever have a great way to switch from one to another. With nearly 10,000 notes in Obsidian, that's becoming a major hurdle!