> For example it is nearly impossible to say, put a box 2/3 of the width of a container of unknown width. Just the simple task of centering an element has pages dedicated to it and to my knowledge, only CSS3 has a reasonably workable solution.
It's been a few years since you used CSS :) Both of these things are trivial to do now
But to be clear: while I think my CSS experience would give me a grasp of what needs to be expressed and some ideas for how to express it, there is a whole other layer of actually applying that, and reconciling it with the content, which would be a challenge (and is done for you by the browser in CSS' case)
> As far as LaTeX's abilities as a programming language go, I have an interpreter for a reasonable subset of C written in TeX (it was an academic exercise but this is just to show what is possible). So it is much more than a mere markup language.
I believe you, but I also question whether that level of power is actually being used by people making documents with it, or whether it just adds complexity. I genuinely don't know. But those are the kinds of places one might find improvements to be made.