These sites aren't fast though... As soon as your computer isn't the newest or your internet connection isn't the fastest, or you simply have other things happe

These sites aren't fast though... As soon as your computer isn't the newest or your internet connection isn't the fastest, or you simply have other things happening in the background, these JS-heavy sites slow down to a crawl where more reasonable things would render instantly. They also make it easier to hide nefarious code and often break accessibility and customizability the user agent is supposed to provide.