It's not sad at all, in fact it's the opposite - Backbone can be considered a stable, battle-tested framework with a "finished" API and features set. What's not to like? Sure, they could turn it into a bloated monster, with constant API changes and new features with new bugs, but Backbone had a clear goal to be as versatile, flexible and easy to use as possible, providing only the most important components, and they've achieved that all right. Seriously, if you've made several big web apps in the past using Backbone than you'll make another one much faster with Backbone, rather than the "new and shiny" which you'll need to learn from scratch.