Well, I'd prefer if it provided widgets that can't be skinned. :-) The theming should be the user's choice, not the app designer's.
> That alone would wipe out an incredible amount of complexity and if done right would make web dev as an experience vastly more pleasant.
I don't really care so much about the web dev experience as the web user experience. My experience as a user is greatly degraded by a bunch of web devs full of bright ideas about how to make their apps look, rather than using predefined widgets whose look is determined by me.
> Much of this complexity comes down to primitives being too primitive for the use case of web apps.
I totally agree with this, although I disagree about what the better alternative is. In my view it is partly this issue that's led to the disappointing profusion of "skinning". In desktop app toolkits you use a tree view, or a button, or a dropdown, or whatever. That widget's "identity" is based around functionality and its look and feel are not controllable by you as the app author. Instead, they're determined by the user's platform (color/font settings, window manager, etc.). That's a better model for users.