You can do pretty neat things with trivial html/css these days, where you needed quite a bit of JS just 5 years ago.
Platform GUI toolkits are designed for controlling an interactive program from the start, a very different usage scenario. They were never designed to be documents to be read from top to bottom. Traditionally, GUI toolkit almost never included fancy text layout boxes just for text display. To give you an example, a simple text label to be used next to a button almost universally could be of a single font with the same style throughout.
I wouldn't even consider this a limitation, because on toolkits with advanced theming (GTK/QT), this allowed for a very consistent layout across all programs, which is clearly a much better user experience for the user as opposed to styled individual applications. Somehow, this crucial bit of /actual/ usability /design/ was lost.
The irony? Current GUI platform toolkits are actually copying the document model of web pages instead, so that your layout skill set can be more easily transferred across systems. So you can finally style your button's label to your hearth's content. XUL is probably the first example of this.
As if "layout" was the major issue in desktop user interfaces (HINT: it's not).
Now we have GUI toolkits which are basically web views that maybe call some native code. In my opinion: a huge failure in engineering and user experience.