I disagree with the title - I don't think this is a sad state at all. This looks very healthy to me. Backbone clearly had a purpose some years ago and it is unequivocally deprecated now. To me, this is a javascript library aging gracefully and opening the way to newer, better libraries. By removing itself from the list of relevant libraries to choose from in the current year, backbone has helped to reduce decision fatigue.

I hope other Javascript libraries and framework follow this trend until we find a handful of "winner" libraries in the same way that each language has its own "winner" MVC library.