It's not just aesthetics, having proper typesetting makes papers more accessible, easier to read and parse, the standard formatting makes understanding the layout of papers easier, there is a huge library of packages that cleanly abstract the task of rendering obscure symbols and complex mathematical formulas, and it automates the job of tracking figure, equation and reference citations to name just a few of the features. Fine, TeX is an ugly language that only a programmer could love, but in over twenty years nobody has yet been able to replace its expressive power and flexibility -- doc generators just compile to LaTeX and more user friendly GUIs like Lyx and TeXMaker have been written to ease the process of writing for end users, but the underlying format has yet to be replaced in over twenty years. Like Markdown, TeX rides the line between being able to be written by hand for greater flexibility and automatically generated for newbies.

Unless you think that reading red text on a blue background in payprus would be an equally enjoyable reading experience it more than simple aesthetics.

You sound like aesthetics is a bad thing you need to disavow for some reason.

> Fine, TeX is an ugly language that only a programmer could love, but in over twenty years nobody has yet been able to replace its expressive power and flexibility

Which doesn't make it less ugly. If we can't cure common cold yet, that is no reason to praise it and making it sound as if it's a great thing. It is a problem and so is the need to use ugly language to produce aesthetically pleasing papers. The fact that we don't have solution for this problem yet does not turn it into non-problem. It just says nobody yet was good enough to solve it.

... did I just read a rant about how enjoyability and simplicity are NOT aesthetics?

Are you related to the author of "The Joy of Tex"?

In my field, equations and diagrams are relevant for 99% of research papers. I would poke my eyes out with a grapefruit spoon if I had to spend the rest of my life trying to do this in Word.