GVG while I do agree that screenshots are very useful, there's also a very good reason we don't have any on most extension: it's a lot of work.
I think all the FoF extension that have screenshots are completely outdated. It's very difficult to keep them up to date. And sometimes outdated screenshots give the wrong idea since they might show features that were changed or removed.
The discussion first post is also often the same as the GitHub README file and it's not always practical to include screenshots in README since they need to be either hosted inside of the repository, or externally but then not all README viewers will show them the same way.
I do hope we can standardize this a bit better between extensions in the future!