I spent some time working with the Sphinx source code (the main user of rst), and found that reStructuredText is very poorly suited for porting to any other platform because a lot of the "spec" is just whatever the Python implementation is doing. IIRC it's also not context-free, so it's more laborious to write a parser. "Technically superior" it is not. I also think a lot of the syntax is obtuse.

That said, I really dislike that Markdown does not have any affordance for adding custom markup. Because of that, it's poorly suited to technical documentation; there's no official way to say "insert the autogenerated docs for function X here." Every doc system that uses Markdown invents its own special thing.

So, I think there's still space for markup languages that find a balance between prettiness and extensibility. I did my own experiment that let you define custom HTML tags but didn't have a reason to really finish the project.