I think completing the rewrite[1] of Tectonic[2] (Rust-powered XeTeX) has bigger potential and it's already working in many cases. [1] https://github.com/crlf0710/tectonic [2] https://tectonic-typesetting.github.io/en-US/
My goal with finl is not to re-create TeX but to reimagine it. The macro-oriented programming language is a big pain point, as are the whole concept of category codes. In many instances, LaTeX is still hemmed in by the constraints of ca 1980 computing technology. If you look through tex.web, you'll see things like weird string concatenations that were done in order to save a handful of bytes of memory. It was a radic…
I don't know if you are aware, but finl has been also submitted to Lobsters (https://lobste.rs/s/udu5oe/finl_is_not_latex_reinventing_lat...). One of the comments mentions SILE (https://sile-typesetter.org/). I looked into it (https://www.youtube.com/watch?v=5BIP_N9qQm4 was nice introduction, although I don't know how up to date it is). It seems to me that SILE replaces many pain points in TeX, while being somewhat close to LuaTeX (and TeX in general), due to use of similiar components (Lua, alogorithms, hyphenation patters, libraries). It even supports "LaTeX" like input syntax, but frankly I don't think that is the part of LaTeX I would keep :).
Can you share your opinion on SILE?