Almost all of these projects are doomed to fail (sadly). TeX is clunky, etc., but it makes really beautiful documents and the math support is ridiculously good.

Almost all of these projects are doomed to fail (sadly). TeX is clunky, etc., but it makes really beautiful documents and the math support is ridiculously good. It's just a very high bar, so people are willing to live with crummy stuff. Even MS Word (a product with many billions of dollars of investment, likely) doesn't make documents that look as good as TeX.