Yes, I want to save the files locally to the disk. I don't use Figma, Slack, Notion, Facebook, Twitter (except sometimes for reading, using Nitter), or Google Docs. You could save the HTML, but that isn't always ideal. Having defined file formats can help, which is the case when using email, NNTP, ActivityPub, IRC, etc.

FTP is no good. There are better protocols, such as HTTP, Gopher, Gemini, Plan9, etc. I had made up a file format for serving directory listings by HTTP (but I don't know how to configure Apache, or to write an extension for Apache, to be able to use it).

About "who think the browser should be for browsing documents and not virtualizing apps", it is badly designed for virtualizing apps. (I have thought of some better ways.)

Also, the file system paradigm does not fail with shared content; you could have the program to mount a remote file system and then access it using local programs, if wanted. (You can then also easily to copy files between your computer and remotely, in this way, by using the standard operating system commands for doing so, and will work just as well with command-line or GUI. Similarly, for SQL databases, you can have an extension to expose remote data as a virtual table, and you can then easily copy data between locally and remotely.)