"Built on top of react", sorry at least for now it is too big of a dependency for most projects that are not react based. IMO that disqualifies it from being "framework for building rich text editors".
The core actually doesn’t rely on React at all, allowing interop with any front-end framework, or even vanilla JS. The current plugins provided officially are React plugins, but other plugins can be built for Vue, Angular, etc.
If you are looking for a completely framework-agnostic rich text editor, then check CKEditor 5 (https://ckeditor.com/ckeditor-5/). It comes with it's own UI library which you can swap freely with any other UI thanks a to highly decoupled architecture.
"Better" is a subjective thing. Currently I use lit-element base class for web components, but I plan to try stencil and vue to see how it feels like. At work we also use react for some projects.