One day browsers will natively support modules and "Bundle Splitting" as the article calls it will just be the intuitive and automatic thing to do. Until then we have webpack.
Vite is one of the first tools I know of taking advantage of this: https://vitejs.dev/
"On demand file serving over native ESM, no bundling required!"
I just launched a small production site using SvelteKit, which now uses this under the hood.
This situation has been playing out for many years and it has only gotten more confusing.