Exploring the possibilities of Backbone.js / React in WordPress core

I stumbled upon backbone.js client in wordpress core in connection to the rest api.

I’m still learning advanced js, but I find it curious how the official documentation is quite limiting for this.

Can it be used to make a full app based on it, or does it just remain to be used to load more posts without page reload?

I found nothing extensive while googling either.

On the similar note, I was also curious about the react framework inside of the wordpress core, and as I understand it’s still limited to gutenberg blocks?

I didn’t understand why is the only option to do a combo of wordpress and react in a form of headless app… I mean why does the database need to be decoupled from the rest of wp, if wp contains an abstracted form of react in its core.

I would appreciate any and every clarification of mentioned subjects or referal to an adequate source of information.