> animations are done in JS instead of smooth CSS transitions, drag and drop support is manually rewritten in JS...
I mean... maybe in some legacy plugins that budget-shops drop into a Wordpress site without thinking. This stuff doesn't really happen anymore in real projects; there's not much point.
> Whenever a feature gets added to standard HTML, web frameworks and "polyfills" keep implementing their own versions because the standards don't fit them and they don't want to rewrite (or keep their own implementation as a mere fallback).
I think you misunderstand what polyfills are. Polyfills exist as an implementation of the standard, before the standard has been fully supported. They get stripped out when possible. In no way are they "their own version" of the standard.
> Even if a data binding framework would be standardized today, it would take years for browsers to catch up and gain critical mass.
It definitely wouldn't. All major browsers get silent auto-updates now, and Chromium alone has over 75% of the market share now that Edge is based on it. Google was the one pushing web components in the first place, and today Firefox and Safari would face pressure to keep up lest they lose ground when more sites become "just for Chrome". The silver lining of the browser monoculture is that features get implemented quickly.
> There'd only be more polyfills and Javascript to help support people running IE11 or whatever.
Possibly. But in today's world polyfills are less and less necessary (see my previous statement). Most companies these days just write off IE and outdated browsers as not worth bothering with. And for all those other browsers, there would be a dramatic drop in the amount of Javascript.
> HTML templates have been introduced and then ignored by frameworks already
HTML templates are the prime example of how useless the web component standard is in its current form: they literally just hold DOM nodes. Those DOM nodes can't appear on the page without being cloned by JavaScript. They gain no special functionality. They just sit there. Templates without databinding are hardly better than an HTML string.