I agree -- I originally wanted a markup language to do away with LaTeX for typesseting but then I realized that getting image sizing and placement right on any markup language is even more painful than with LaTeX, so I just never jumped ship.
I still wish I had a publishing toolchain that produced multi-format output (HTML5, docx, ePub, Kindle, and plain text) from the same source file. It can be done with LaTeX sources but the result is sub-optimal.
As I wrote in another comment, this can be done quite easily with Pandoc. It is a really powerful processing tool and with the right set of templates it can do wonders. Have a look at Kieran Healy's work: https://kieranhealy.org/blog/archives/2014/01/23/plain-text/
For some definitions of "easily". For a programmer, yes.
For an enterprise organization with a full gamut of technical ranges from "maintain 40 github repos for fun" to "I still don't trust anything but Word, Excel, Powerpoint and email", pandoc is not the solution (as nice a tool as it is).
I still wish I had a publishing toolchain that produced multi-format output (HTML5, docx, ePub, Kindle, and plain text) from the same source file. It can be done with LaTeX sources but the result is sub-optimal.