LaTeX needs replacing with something faster and more program-y, and that isn't just a python script.

LateX's successor should be opinionated, safe, easy to build in parallel, and also good at integrating with other tooling:

Let a CAS generate the next equation for you, for example.

Make sure that figure is never out of date (e.g. a build system rather than relying on a web of files and button clicks)

Etc.

This will likely never happen because latex is still very good at what people want it to do push comes to shove, but we could have a much better document format and publishing system around it.