It isn't security I'd be worried about. I'm sure there is some real wizardry in the formatting algorithms and many bugs related to it fixed over the years. Rewriting the TeX engine would just be a huge effort to almost certainly arrive at an inferior and incompatible clone.

I agree, "safety" is just the most common reason people give for rust rewrites, so I'm assuming that's part of their rationale.

That is why stuff like pandoc exist. A more modern latex.

Pandoc seems to exist only to support moving from one markup language to another. And markup languages seem to proliferate when people decide to trim down the options from what they had been using. Only to build them back up to the point that a new one is formed, to trim down the options.

Which is ultimately frustrating if you ever try to go back to an old document, and realize you don't have the exact markup engine that you used back then, so that you can't actually rerender it.

Now, to be fair, often this is ok. In particular, you might not care about how it rendered before, and a minimal markdown is fine.

However, if you do care about presentation, it is maddening.