I've read the web app and it seems to me it is just https://backbonejs.org/ re-written in Typescript and allows JSX.
I'm very certain Typescript and JSX will have improved the DX for Backbone like apps, but it doesn't address all of the other issues that teams had with Backbone.
e.g. Cyclical event propagation, state stored in the DOM (i.e. appendChild is error prone in large multi-person code bases), etc.
FWIW, the reason this works for eureka is highlighted best on this page: https://github.com/wisercoder/eureka/graphs/contributors there is only a single author!