A modern TeX would probably look a lot like SILE:

Simon's a smart guy. It's a pretty neat project.

On Fri, Oct 4, 2019 at 9:13 AM Jon Forrest <nobozo@gmail.com> wrote:

One slightly OT fact about TeX. On my 16GB, Core i7, SATA SSD
Lenovo T430s laptop running Fedora 30, it takes ~3 seconds to run TeX on
the ~900 page TeXBook. That's pretty fast. TeX contains all kinds of
code to make it fit in the constraints of a 1980s computer. I wonder
whether a redesign for a 2020 computer would be faster or slower.

I suspect, but can't prove, that classic [nt]roff might also
benefit in the same way. groff was written latter, so it might
suffer less.

Jon