I like many of the state of the art frameworks, especially backbone.js and I'm really thankful for how much impact they had on making complexity in web apps manageable. That said I absolutely agree with you regarding the fragmentation problem which seems more like a stack problem to me.

For me personally it looks like what the web desperately needs is a common ground for how widgets work and behave. Web Components look like what we will get and I really can't wait to see that happen: https://dvcs.w3.org/hg/webcomponents/raw-file/tip/explainer/...

Here are some examples from Dart Web UI (web component polyfills for Dart) http://www.dartlang.org/articles/dart-web-components/

Also here is a great article about the web stack fragmentation that you might be interested in: http://zef.me/4835/dart-web-fragmentation-vs-web-development...

Exciting times, Thomas