It's already done! Web Components (Custom Elements + Shadow DOM) are web standards, ratified by W3C, and they already work great in Firefox and Safari. This whole article is simply incorrect.
http://w3c.github.io/webcomponents/spec/custom/ https://w3c.github.io/webcomponents/spec/shadow/
https://www.webcomponents.org/ see "Browser Support"
Therefore there was some conflict between the two groups until WHATWG emerged victorious. Here's the final agreement: https://www.w3.org/2019/04/WHATWG-W3C-MOU.html
It boils down to complete capitulation by W3C.
They cannot be serialized, they break accessibility, they break screen readers (AFAIR), they are not lazy loaded, they do not participate in form events, they...
But they work fine in screen readers, (you can screw this up with JS, just like any other HTML) and they "participate" in form events just like other HTML.
Since they require JS, you can lazy load them if you want (it's just JS).
Shadow DOM also throws off accessibility IIRC if aria-labeledby and similar cross shadow dom boundaries [1] but I do agree they should be largely accessible to assistive technologies.
You can't truly lazy-load them. See Rich Harris' (author of Svelte) take on Web Components [2] And these two articles by a Web Components proponent listing the many issues they still have [3]
[1] See for example this tweet https://twitter.com/sarahmei/status/1198069119897047041
[2] https://dev.to/richharris/why-i-don-t-use-web-components-2ci...
[3] https://dev.to/webpadawan/beyond-the-polyfills-how-web-compo... and https://dev.to/webpadawan/the-journey-of-web-components-wron...
Screen readers especially only do well on simple documents, and only work with apps well they’re specifically designed to interface with which for the most part are apps that are used in document creation or text communication like Word, or Skype.
*Disclaimer: “well” is in the eye of the beholder. It’s challenging to use them with arbitrary apps, and the time investment is only useful if that app is going to put food into your table.