Thanks for the feedback, the web UI does have a gallery link [0] with a few interactive examples [1]. I agree though, a screenshot like this would be a good addition to the homepage.
Yes, that's roughly accurate. Jan Pöschko (the creator of Mathics) went to Wolfram in 2012 and I went to Google at the end of 2016. Since then it's been largely unmaintained as I don't have the time to work on it unfortunately
[0] https://pasteboard.co/IdIaJNo.png [1] https://pasteboard.co/IdIc7dc.png