[alerighi]

Why rewrite TeX? To me TeX is one of the example of what a software project should aim to be, arrive to a stable version where it does what it should do and it work reasonably well. That was the initial idea of Knuth (in fact the version is a number that approaches PI one decimal at a time).

This is the contrary of the "modern" philosophy that says that we need to constantly modify, update or rewrite a software in "modern" languages even if it's a huge effort and risks introducing bugs that were not present in the original version.

Well, at least if we want to rewrite it let's just have to wait 10 years, then we can fed all the codebase to ChatGPT and ask for a new fancy Rust version!

Regarding of integration, TeX follows the (to me still relevant) UNIX philosophy that a software can be called by another software and the input/output communicates in a pipe. Nowadays we have even containers that let us distribute the software as a single unit so we don't have to worry about installing multiple files on a system. Not a big deal, in the end.

[jhanschoo]

I don't think you realize that

1. Most people aren't compiling with tex->dvips->ps2pdf anymore, most people with basic requirements compile with pdftex for more robust hyperlink and navigation pane, etc. features

2. People who want Unicode support and support for modern font files are using xetex or luatex

3. What has been proposed isn't a new tex compiler but more like a package manager for 3rd-party tex packages, using the already established xetex compiler to compile. Whereas historically you would download the whole distribution (or a predefined subset thereof) onto your system versioned by year (e.g. TexLive 2020) eating up GiBs of space, this allows you to download just what you need for your document.