What a great summary! Unfortunately, many discussions of TeX vs alternatives are somewhat thin on details and are instead trading on emotions. As you mentioned in your comment, the choices made by Knuth are far from random. He even made it possible for anyone to change them! Not many people using TeX know that the choice of the backslash as an 'escape' character may be easily changed. Even the necessity of curly braces may be avoided using carefully designed macros. LaTeX took a different path but it is only one possible choice. It is telling that no real alternatives have emerged during the 40+ years of TeX's existence.
The way I see it, this only proves my point. As you write: '...None of them have become the standard...' and this is at the center of the argument. TeX may not be ideal but it strikes the correct balance to become and stay standard for so many years. One can do pretty much anything in bare Postscript (and I am ashamed to admit, I have) or even 'handmade' PDF but it does not make it a good alternative to TeX. I have experimented with alternative syntaxes (apologies it this is not the correct plural of 'syntax') but had to give all of them up due to a number of flaws. These experiments gave me a new appreciation for Knuth's choices.
I disagree. I think Latex will soon become legacy like Cobol.
HTML and CSS basically do a lot more than Latex does - except for maths things - and are far more widely known, and far more forgiving. Also importantly, they support hyperlinks, animations, and inline interactive scripts. It seems that HTML and CSS with the appropriate CSS styles and shorthands (like Markdown) could eat up everything that Latex does and much more. I don't know if Latex can survive the onslaught.
I have heard HTML/CSS mentioned as an alternative and I pray every day this time will never come. Even taking all the complaints leveled at LaTeX at face value, using HTML/CSS looks like pure hell to me. Allow me to elaborate.
1. You mentioned forgiving. One may not like the style of TeX error messages but its tracing facilities are extensive and given enough time and perseverance one can track nearly any layout issue down an correct it. Compare this to CSS silently ignoring incorrect syntax, having different syntax across browsers, etc. I would take strict syntax checking over this mess any day.
2. Many complained that LaTeX has more than one way of achieving the same result. True but how many ways are there of centering a div on a page? I can list six off the top of my head and there are probably more.
3. You casually mentioned '...except for maths things...' but this is far from minor. I cringe when I read engineering papers not written in TeX: the formulas are so ugly that they border on unreadable.
4. CSS may be wider known but unlike TeX CSS is a moving target. Being designed by a committee it carries all the flaws, like kludgy design in the name of 'compatibility', poor choices of syntax to make it appeal to a wider audience, etc. The designers of CSS are so enamored with the 'cascade' but in practice it is rarely used as intended. The 'important!' kludge as a perfect testament to this.
5. LaTeX syntax may be unappealing to some but HTML takes it to a whole other level: whitespace that affects the layout yet no easy way of getting rid of it (HTML style comments are a torture device); too verbose... one may not like the backslash but what about <...> </...> ? Five extra symbols!
6. LaTeX engines produce full featured PDF so hyperlinks are not a problem (most LaTeX documents have them). Yes, CSS has so called 3D graphics but it is anything but programmer friendly. What good are 3D transforms if one cannot even use simple lighting effects programmatically; c'mon, at least give me Lambert reflection! Incidentally, inline JavaScript can be included in pdf documents produced by LateX as well (although ... why?)
Academia has got inertia. How long has it taken it to adopt Open Access? There's far more investment into web tech than into Latex. Browsers can do more than PDF readers.
The “except for math” part is doing a lot I think. There’s a huge amount of work needed to get rendered math to look as good as latex’s and I’m not sure CSS (as an example) is expressive enough to get this done
The LaTeX formula language is a separate thing from the rest of LaTeX: It's become the standard for formulas. There are some editors that can speed up writing those formulas. Asciidoc also offers an alternative formula language.
It tells me that beauty is in the eyes of the beholder, i.e. what one may perceive as ugliness, countless others will view as beauty or, at least functionality. I personally think that the ugliest design in existence is Python but I admit my opinion is not common. Moreover, I use Python myself, since syntax is not the only important thing in a language (the ecosystem is Python's undisputable strength). It is also unclear to me what specific 'ugliness' in TeX is fixed by, say TeXmacs. Is TeXmacs internal language dramatically (or any) better than TeX? Does not seem so. The WYSIWYG option? There are WYSIWYG editors for TeX as well.
"here are WYSIWYG editors for TeX as well." not there are not. Apart from TeXmacs I know of no editor which give you on the screen the same result you get on the paper. LyX has not such a feature. If an approximation is ok, then fine, but I do not think you can call it WYSIWYG. Is something else. And it requires a lot of work to do it correctly. You should at least appreciate the technical merits, even if you prefer to use LaTeX for its ecosystem. But as a user of both I see the clear merits of TeXmacs in terms of quality of my work (mathematician), I can focus more on what I'm doing, instead on deciphering the mess of the LaTeX formulas and try to find where to put a correction. I can give online lectures with it, discuss on zoom while scribbling on a TeXmacs document, much of the work I was doing on paper I do now directly on the computer. To me there is a clear difference in the user experience between TeXmacs and LaTeX and I will never go back to write LaTeX if I can help it (I do it sometimes, if my coauthors are using it and do not want to try otherwise).
As a fellow mathematician you may then appreciate the fact that local and global maxima may differ dramatically which pretty much precludes true WYSIWYG (not just in TeX) in that you have to settle for one of the two: visual output with suboptimal aesthetics (TeXmacs, and, to some extent, LyX) or perfect results that you have to compile with some delay. It has nothing to do with the computational power available but rather with the occasional highly unstable line breaking. Even in MS Word it is annoying sometimes to see it resize a current line even though it uses a rather lame line breaking routine. TeX does have facilities for almost real time WYSIWYG (SyncTeX was added specifically for that purpose) although they take some effort to set up. As far as concentrating on the work at hand I have written whole papers without compiling the document once before everything was complete. I admit it takes some getting used to but I prefer something I can grep through to a mere pretty picture. I admit if my work was heavy on large commutative diagrams I might have had a different view. One thing I totally agree with you on is that TeXmacs is an outstanding piece of software. I would just prefer to keep my documents in TeX (which TeXmacs can export, kinda).
> visual output with suboptimal aesthetics (TeXmacs, and, to some extent, LyX)
Till now I took the developers word that the aesthetics of TeXmacs is better than the one of TeX and I would be curious to know where the opposite is true (and in case also why this cannot change)
From what I have seen in TeXmacs documentation, they have implemented pretty much every feature of TeX's linebreaking algorithm and more (microtypography, global page breaking, etc) so my claim above was not to say that the documents TeXmacs outputs have suboptimal aesthetics (to be fair, modern versions of TeX have all of these features, as well, although not the original TeX, alas). What I meant to say was there is no (even theoretically) possible way to have a perfect WYSIWYG editor if global paragraph/page breaking is desired. For example, due to global page breaking, one may be editing a line in the middle of the document and its position on the page (and the page number, left/right headers, etc) will be constantly changing---not good for the visual experience. I do not know how TeXmacs deals with these (extremely rare, admittedly) cases but the discussion was about the true WYSIWYG vs not so take it with a grain of salt. Let me say this again: TeXmacs is an outstanding piece of software. If in thirty years, a TeXmacs file format is still readable by the newest version (possibly with some easy tweaks), I will consider switching from TeX :). My other (minor) concern is that the LaTeX files that TeXmacs exports do not render at all as the pdf files TeXmacs produces itself. So as a WYSIWYG frontend to LaTeX, TeXmacs is ... not quite. Which they never claimed to be so I cannot fault them for this.