That's exactly my experience as well. I recently worked on two "enterprise rich web apps"(I hate that term) that were desktop-like.

App A: the UI was mostly composed of HTML glued together with JQuery components, with a custom Model/Controller implementation (similar to Backbone.js) for the data. The view did have a lot of glue, but the data separation ended up a lot cleaner, and was easier for designers to maintain (HTML/CSS).

App B: Was taken over from another team that used ExtJS. App B, had full UI without much effort, but ended up with a lot more cruft and direct view/model dependencies.

Plus the ExtJS documentation is terrible.