Backbone is small because it doesn't do that much. After learning Backbone I regretted wasting so much time learning how to do simple things like nest views correctly. Backbone made me really long for a complete and opinionated framework.
Sencha gets a lot of flak, but IMO it is the most mature, built out framework you can get. You get, out of the box:
1. MVC/MVVM structuring
2. a DOM abstraction, which albeit requiring a lot of learning, works once you grok how to use it (something that can only unfortunately come with experience)
3. Touch driven gestures
4. History and repetitive task management
5. A grid view that's unparalleled in the market.
And that's just for starters. It's downsides include a steep learning curve and a classical inheritance model, but those should hardly be blockers to anyone willing to invest the time it demands.
