GeoffreyLitt wants collaborative documents to be client-neutral : https://www.geoffreylitt.com/2021/03/05/bring-your-own-client.html
A good overview of the issues and problems. I'm not sure it leads anywhere particularly new or promising.
Yes. There are major tensions between standards and innovation. By definition, if you share standard data with other apps, you're restricted to doing what the other apps do.
Or you share some low level infrastructure (ie. "text").
See also :