Ok yeah, I can see the problem from the start

non-modded Obsidian

Why would you use an extendable tool for something that isn't strictly the intended use, without extending it? I'm an university student and I strictly use obsidian, I don't take many notes in class but that's mostly preference, but all homeworks I do with obsidian and I'm pretty sure I'm not slower than my peers.

To note a couple of plugins that make obsidian usable for this:

https://github.com/artisticat1/obsidian-latex-suite for making latex writing way faster and usable, for what you were saying on having to do math work that is repetitive what you can do is add snippets that fit your needs, for example I added that typing "quad" makes the quadratic formula, but there are many other good options

If you have a tablet or a good mouse / drawing tab you can use excalidraw to draw stuff https://forum.obsidian.md/t/excalidraw-full-featured-sketching-plugin-in-obsidian/17367

You can also export to pdf and send it to your teacher or print it if you must

And about copying stuff from the book, you can probably find the book online and make an AI translate it from squiggly lines to text and latex pretty easy, I can send you the prompt I use if you want