> By "at scale", I mean building abstractions on top of commonly used html elements and making them interactive,
This sounds like double-speak. That's not what at scale refers to, even allowing a very loose definition.
How the HTML is generated is moot. Server side templates had re-usability at a "component" level.
iFrames exist, redirects exist.
I'm not saying all JS is bad. I'm saying too may new people seem to think JS in and of itself is magic and there is no other way to generate/manipulate the DOM or talk to other computers.
I'm bailing out of this conversation now because you're heavily conflating HTML, browser functionality and www fundamentals with website builders(i don't know why you felt the need to qualify it with "professional")
> Even HN has JavaScript for that little bit of interactivity (collapsing comments).
Yeah no, "even HN" works perfectly with JS blocked. JS for HN is an enhancement, not a requirement. They understand how the web can work...