Busy reading this and it's great so far. One comment, you've referenced "tree shaking" a few times without explaining what it is. I think I know but it might help others to explain that before your reference it.
Dead code elimination in its traditional form also runs during code minification, which is a separate build step from bundler tree shaking. Having separate terms avoids ambiguity.
A practical example would be that tree-shaking wouldn't remove the variable b in "export function foo(x) { let b = 10; let a = 20; return x + a; }" but if this export isn't imported anywhere, then it would remove the whole function definition. Uglify.js, which does dead code elimination would remove the unused b variable.
I struggled with the ordering since each section is somewhat mutually dependent; this is arranged more like a thematic history than a chronological one.
Tree-shaking naturally fits under bundling, and I'm afraid that explaining it earlier will make tree-shaking's explanation itself contextless since without bundling there is nothing to tree shake.
I can hyperlink those references to the tree-shaking section tomorrow so that there is an action for the confused.
Not to take away from the excellent writing in your original essay!
Thanks for the response and more importantly the article! It covered exactly all the points that were opaque to me about frontend build processes. I've also forwarded it to a couple of other backend devs that I know.