What has to be "standard"? The application itself or its UX? I'm pretty sure it's the latter, so all it takes is a familiar UI and low-friction approach. You don't have to be a world famous brand for people to be able to use it.
Exactly. We only need a "standard" because everyone builds walled gardens and easy content distribution to multiple platforms is intentionally difficult. Right now you have to watch a "YouTube" video, instead of just a video on YouTube.
Standards != centralization. Standards apply more to protocols, and centralization applies more to ownership of data.
For instance, there is an enormous benefit to the entire world from using a standard IP/TCP stack. Yet, we don't seem to suffer from a centralized authority making controversial or conflict-of-interest decisions regarding that stack.
So what I was suggesting is that document-editing abide by some global protocol/standard, which would include storage, versioning, and permissions. As far as the choice of user-facing interfaces and implementations of logic around those standards, there need not be just one, or even a few. Everyone can bring something cool to the table and anyone can use whichever flavor they wish.
To avoid Google Drive/Docs/etc you don't have to boil the ocean. Buy a Synology DiskStation and just use the included software
It's a solution that works for anyone with basic IT skills. Offer your extended family access, and use the provided software to control permissions etc
Also, non-powerusers will gravitate towards the simplest solution to their problem, and that will also tend to be the one that the highest number of people understand how to use.
