This is incredibly true and something you don't realize until you're browsing the web on a slow connection.

I was travelling with 2G and using most client side apps was near impossible. One app sent down a 1.9MB `components.js` file, and because it was a JS app, all scripts had to be loaded until anything rendered.

Obviously server-side apps are in no way immune from this, but by default, unless you really do need a rich client experience, it's often not worth the bundle size and CPU load. Just send down HTML.

You know which website works fabulously over 2G? Hacker News.