Well, first of all, this tool also works with Dojo Toolkit, SproutCore, YUI, Google Closure Library, qooXdoo, etc. The key take away is that if you are doing anything more than splashy webpages with animation, then you will need to work with a framework (like all of these) instead of a toolkit (like jQuery).

The same thing happened on the server side some time ago when people just wrote some html home pages with some scripting tags (aka PHP). Eventually, when you start to create something complex, people started using some "scripts" and then eventually started doing MVC and the like on the server. Keeping with PHP, this means that people started using Zend Framework, CodeIgnitor, CakePHP, Symphony, YII, etc.

Some people complained that it was too much for lowly HTML, but time and capabilities advanced anyhow. Now that time is coming to the client, thanks to faster browsers, and HTML5 local storage. And mobile. Latency and offline mean storing things locally, and that means business logic at the client.

Prepare to love our JS framework overlords.

To make this tool, I dealt with all the frameworks listed. All have some flaws. ExtJS has copious markup (and CSS), and some non-optimal layout choices. ExtJS4, which you can download a preview of, has dealt with them. I admit, there is some of my ideas in there they ran with. One I did not propose, but (like Closure) they are using in v4 is rendering based on browsers. Old browsers get the copious markup so a real and good looking UI will be possible. And where it can be done in CSS3 instead, they use far less markup. The fast browsers become even faster.