In my book Resilient Web Design, I quoted Wilto:
Lots of cool features on the Boston Globe don’t work when JS breaks; “reading the news” is not one of them.
That’s an example where the core functionality is readily identifiable. It’s a newspaper. The core functionality is reading the news.
In those particular cases, I actually do. I believe that a textarea in a form would do the job nicely. But I get it. That might take a lot of re-engineering.
So how about this compromise…
Making this distinction between read-only mode and read/write mode could be very useful, especially at the start of a project.
Now start adding the read/write functionally. You’re enhancing what’s already there. Progressively.