It's a hard drive. It's talking to the controller at 300MBps, but it can't reach that. For single drives, we've always been able to keep the interface well ahead of the drives, until fairly recent SSDs. New HDDs can do >150MBps sequential, and >2MBps random.
On my main rig, Flashblock is less for performance than it is having a guaranteed play button under my control. But, it helps on lesser hardware quite a bit just in performance, much like adblock. In any case, the link the OP gave is not most sites, but also isn't the worst news site I've ever seen. I can handle most sites on my phone, as long as they aren't too ridden with 3rd-party ads, faking a desktop UA (often better than using the mobile versons), and my internet connection is usually the bottleneck for my PCs (~50-100ms per file, even with pipelining, adds up when there are tons of files to get). It's places like the OP's link, Blogspot blogs, and other giant hubs of Javascript, masquerading as individual websites, that can hog CPU time on anything, but become quite sluggish on old/slow PCs.
Inefficiency. Many people hunt and peck on the keyboard*, and have to 'retarget' every time they move the mouse. When every action takes a minimum of 3 seconds, the difference isn't as much as to those of us that are moving in expectation of certain software and hardware responses.
Thanks 🙂
