> the real ones use Typst now
Are you intentionally leaning into the exact caricature I'm referring to? "Real programmers only use Typstly, because it's the newest!". The website title for Typst when I Googled it literally says "The new foundation for documents". Its entire appeal is that it's new? Thank you for giving me such a perfect example of the symptom I'm talking about.
> TeX and family are stagnant, difficult to use, difficult to integrate into modern workflows, and not written in Rust.
You've listed two real issues (difficult to use, difficult to integrate), and two rooted firmly in recency bias (stagnant, not written in Rust). If you can find a typesetting library that is demonstrably better in the ways you care about, great! That is not an argument that TeX itself should change. Healthy competition is great! Addiction to change and newness is not.
> nobody uses infinitesimals for derivatives anymore, they all use limits now
My point is not that math never changes -- it should, and does. However, math does not simply rot over time, like code seems to (or at least we simply assume it does). Math does not age out. If a math technique becomes obsolete, it's only ever because it was replaced with something better. More often, it forks into multiple different techniques that are useful for different purposes. This is all wonderful, and we can celebrate when this happens in software engineering too.
I also think your example is a bit more about math pedagogy than research -- infinitesimals are absolutely used all the time in math research (see Nonstandard Analysis), but it's true that Calculus 1 courses have moved toward placing limits as the central idea.
>My point is not that math never changes -- it should, and does. However, math does not simply rot over time, like code seems to (or at least we simply assume it does). Math does not age out.
Just in the same sense that CS does not age out. Most concepts stick, but I'm pretty sure you didn't go through Στοιχεία (The Elements) in its original version. I'm also pretty confident that most people out there that use many of the notion it holds and helped to spread never threw their eyes over a single copy of it in their native language.
> I'm pretty sure you didn't go through Στοιχεία (The Elements) in its original version
This is like saying "you haven't read the source code of the first version of Linux". The only reason to do that would be for historical interest. There is still something timeless about it, and I absolutely did learn Euclid's postulates which he laid down in those books, all 5 of which are still foundational to most geometry calculations in the world today, and 4 of which are foundational to even non-Euclidean geometry. The Elements is a perfect example of math that has remained relevant and useful for thousands of years.
So that's it. Just because new languages and framework are rising and fading away, it doesn't mean there is nothing kept all along the way. It just that specific implementation is not the thing that people deem the most important to preserve over time.
> The website title for Typst when I Googled it literally says "The new foundation for documents". Its entire appeal is that it's new?
It might not be the best tagline, but that is most certainly not the entire appeal of Typst. It is a huge improvement over Latex in many ways.