Amicus engineer here. It's actually built on top of Backbone, in a similar vein as Airbnb's rendr. It allows our front-end to be pre-rendered on the server, and sent to the client as static html, as well as some other cool stuff.
> Are the existing libs so bad everyone has to reinvent the wheel constantly?
To actually answer your question: yes.
Existing libs for building large scale apps are in a transition period from server-side only apps to something more akin to native apps, and no one has come up with a great way to do it yet.
Honestly I hope people keep "reinventing the wheel". Web Development isn't in a place where we can just accept the state of the art and call it a day.