Texinfo ultimately gets the @ convention from Brian Reid's Scribe[1], as developed at Carnegie Mellon during the late 70s and commercialized by Unilogic[2,3] in the 80s. Coincidentally, there was a close derivative of Scribe called Mint[4], also developed at Carnegie Mellon in the early 80s for the PERQ (an early personal workstation competing in the category of things like the Sun-1 or Lisp Machines).
What about Typst? Looks to me as a valid TeX successor with a streamlined syntax and much better programming abilities without the limitations of 1977/1982.
Typst is on my list, I wanted to have a look at this year, but unfortunately no time and no need. Except for one letter every one or two years I did not use LaTeX since my diploma thesis.
Unfortunately, Lout never really took off, but I have fond memories of it. I liked it more than LaTeX, too.
[0]: https://wiki.archlinux.org/title/Lout