> It's really frustrating: all articles on accessibility mention the alt attribute, and that you should use them. But few give guidelines on how to write a good alt attribute that is actually well thought out.

You're not alone in feeling this frustration. In fact, this very article includes what I presume to be a screenshot of some code from the React docs. I have to presume that's what it is, because I'm a screen reader user and they haven't provided an alternative, screen reader-accessible version. Go figure.