You probably hate bootstrap and jQuery, as I do, but if you block CDN paths for these libraries, you'd probably never see the internet as it was intended.

Side note: web devs, please learn media queries, vm and em for font sizes, and etc. You really don't need complicated stuff, browsers already have your back, I promise.

Let me tell you about that customer of us, making 60% of our traffic and revenue, using IE11.

Let me speak up for jQuery! It was excellent at the time and made a lot of new UI functionality very much easier to do. Even now, I'd expect a jQuery site to work properly on all devices, whereas some newer vanilla sites are distinctly iffy. As a consumer, I find myself having to switch browsers to get things done significantly more often over the past couple of years.
Lastly, obvs, nearly all web devs use media queries, grid, flexbox - hence sites work on phones.

Honestly I've no idea how much electricity could be saved if every web dev took the time to learn modern CSS, I still see so much code to implement things that you no longer even need JS for, and I'm as guilty as anyone else.

@MM83 probelly a lot. Look at any popular website and see how much is actually used of the shipped mess.

Most of the time less than 20%.