Elevated is one of the most atmospheric, cinematic demos I've ever seen, and the fact that it takes only a fraction of the disk space of the icon used to represent it in the file-manager is ridiculous.

Demos of this caliber are like F1 cars from 60 years ago: a single genius, or small team, creating something totally beyond the reasonable expectations of everyone who is familiar with the technology in question.

I really hope it continues to be possible for this art form to exist.

How would one even learn how to do something like this?

I feel like I have a high level understanding of most parts of the stack, but graphics programming has eluded me thus far.

Would writing a ray tracer be a good starter project? I know I've seen it recommended by several people before.

For basic 3d graphics rasterization concepts and implementation check out 500 lines C++ TinyRenderer and its wiki here: https://github.com/ssloy/tinyrenderer and the 100 lines Python version (only numpy dependency) here: https://github.com/rougier/tiny-renderer

Raytracing in a weekend is also useful: https://raytracing.github.io/