Yjs is being quite heavily used in the industry[1], and being researched by even more companies. There are also demos showing how to integrate it with an existing rich text editors[2]. If you have some ideas about the missing parts, you could also open topic on discuss.yjs.dev - the documentation page (https://docs.yjs.dev) has tons of useful links thou.

Re. other purpose projects - Yjs/Yrs main target are sequential data structures (text, arrays), but it also has support for maps and xml-like elements. In general you can build most data structures with it. I agree that it would be nice to have some other applications in demos though.

[1] https://docs.yjs.dev/yjs-in-the-wild [2] https://github.com/yjs/yjs-demos