LaTeX is not "old trash". It's one of the best piece of software ever written. Just don't import bs in your document.
Tex/LaTeX are completely syntactically extensible. For example, a logician might want to use the software with any number of their notations, or a physicist drawing Feynmann diagrams, etc. I think at one point Lillypad used it for typesetting sheet music.
Edit: i found it! https://typst.app/docs/guides/guide-for-latex-users/#package...
But code syntax can not be changed an no you can't redefine if @ is a letter or not and flip flop that in your code like latex does.