Earlier quoted context omitted.
But then is the Lua scripting at the user level? Can it be used in the building of documents? Or is it a scripting language for the underlying engine, invisible to the end-user? Incidentally I went looking for what pure TeX actually looks like as most people say TeX when they really mean LaTeX. Here's Knuth's TAOCP Volume I errata: http://www-cs-faculty.stanford.edu/~uno/err1.textxt Talk about Perl being line noise..…
I did a few times. It's actually easier to make something look exactly the way you want it to look in plain TeX than fight with some poorly documented LaTeX package.
My experience of using LaTeX compared to WYSIWYG is that it's easier to focus on the text in the editor instead of fighting with the UI interface but it then requires some chasing around package bugs and compile errors. In total it's clearly a net positive for me.
Writing pure TeX would seem to push the tradeoff quite a bit, having so much distracting stuff around the text that requires a totally different mindset than the text being written. It was probably designed for a world where typesetting was done as a final step before publication, potentially by someone else.