Let’s say you want to take a look at Dinamo Zagreb’s squad on Transfermarkt (https://www.transfermarkt.com/gnk-dinamo-zagreb/startseite/verein/419).
Default page load (in Chrome): 7.9 MB transferred
Page load with blocking of non-critical scripts* (in Firefox): 1.68 MB transferred
*The three critical script domains for this website are transfermarkt.com itself, tmsi.akamaized.net, and tmssl.akamaized.net.
So just by blocking non-critical scripts, the data usage goes down -78,7%.
Scripts are one thing, but videos are more annoying. Every news website seems to have autoplaying videos that no one ever asked for. I really really wish browsers would offer a way to block media elements. Not all this "we'll try to detect whether blah blah and maybe don't autoplay if this and that" nonsense. No. Not these pathetic half-measures. I want a switch that makes the browser forget what a <video> means. Such that it would treat it like an unknown tag. That's the only way.