I guess the block-based document editor field is heating up. With this tool's native iOS and macOS apps, I hope they either unseat Notion, or launch Notion into making native tools. Their web-based UI has extremely poor performance.
I had the same thought. Bear is in this category too. The only differentiator vs. Notion right now seems to be a native app, however. I'm going to give it a try and see if I like it though.
One significant difference is automatic back linking (bi-directional linking). Craft looks a bit like Notion but it has some of the functionality of Roam and Obsidian. Plus, decent native apps, which Notion and the others lack.