To quote Knuth [1] describing TeX “Think thrice before extending,” because that may save a lot of work, and it will also keep incompatible extensions of TeX from proliferating.

Personally, I am of the opinion that the original TeX was well 'modularized' in 'Pascal Procedures' [1], being Turing complete, extensions such as the LaTeX format and the countless of packages after that helped it survive and prosper. Think of a macro that you define as an easier way than programming a module in JavaScript and it doesn't need a half a dozen tools to set it up.

    \def\#1{\TeX\ is alive says #1.}

Nevertheless, provided the lessons learned are incorporated I applaud any new initiatives in more modern languages. Whatever is produced will however, need to be able to parse TeX, otherwise it will not be easily adopted by the community.

[1] http://www.tug.org/texlive//devsrc/Master/texmf-dist/doc/gen...