There are already free / free-ish clones of Roam:

  * org-roam: https://github.com/org-roam/org-roam
  * Obsidian: https://obsidian.md/
  * Athens: https://github.com/athensresearch/athens

+1 for Obsidian. Lots of refinement in such a young product. It has been my main driver recently. I picked it up primarily to keep things local rather than rely on an internet connection. Even so, took only a few minutes to add encrypted backups to S3 debounced on file change.

Great UX makes a world of difference. UX is about more than just features or appearance: it's about everything coheres together as an experience for users.

UX should be relatively easy to copy, but it seems (at least to me) that many people have a hard time copying UX. Many people will copy features or appearance, but their execution usually lacks something. This is not a dig: most people don't get it.

There are a few people who do, and when they create something new, only afterward does it seem so obvious.

This is just my take.

I don't entirely get it either, but I get the motivation for a startup to try it even if it doesn't necessarily add value.

For one, people download and use note apps, so I think there's an inherent curiosity about whatever the next one is. And if anyone can get a critical mass to the point that it's a de facto note-taking app for 'most people', people might become accustomed to the idiosyncrasies and add-on features that the 'winner' note app provides.

There's no good reason for there to be a 'winner' note taking app, but I also don't think there's any good reason for there to be a winner video conferencing tool, or a winner office suite, but we have those.

Videoconferencing is inherently a group activity - it has a pretty clear network effect. Office suites less so, but MS did a good job of using the file format as their moat for quite some time - https://hackernoon.com/complexity-and-strategy-325cd7f59a92