The content of [1] displays immediately for me (and I do not have document scripts enabled). There are <amp-...> elements; I don't know what they are, and they

The content of [1] displays immediately for me (and I do not have document scripts enabled). There are <amp-...> elements; I don't know what they are, and they do not do anything. For webpages that do hide everything, I define my own CSS overrides which prevents the <html> and <body> element from ever being hidden, opacity less than 1, or similar. Further rules can be added to prevent <body> from being animated or having transitions. What is wrong with just HTML, without CSS and JavaScript, or in some cases just plain text and not even HTML?