One of the biggest flaws of the current web technology stack is the unholy mix of concerns with respect to layout. Layout is handled by CSS and HTML in a way that drives people crazy. I recently wanted to have a scroll bar for super long text inside a table cell. Easy, right? Turns out you need to change the HTML to include a <div> inside the table cell, since there is no way to style the table cell itself and have it do what you expect it to do.

XLST doesn't solve this at all, since you're just generating more of the problem, i.e. more HTML and CSS. It feels like there should have been some sort of language exclusively for layout definition that doesn't necessarily know about the existence of HTML and CSS beyond selector syntax.