Reader view is already half way there, and it is as mainstream as it can be, as it comes on all iPhones and Macs. But you're right, my idea doesn't have much to do with the underlying protocols.

Speaking of branding, marketing and UX design, I would say that most businesses have already completely given up on that, and are content to sell their stuff online through portals that are completely controlled by third parties such as Amazon, Booking.com, Doordash, Instagram, etc. Very few make a decent effort to have a website where their customers can easily purchase their products, even though it isn't hard at all.

Could a user-centric browser extract the HTML results of everything made by javascript and present it in a standardized way? Because text, images and videos are already solved problems with reader view. The interesting part would be if HTML input elements could also be thrown in, even though they're usually quite javascript connected. Any website more complicated than that is more of a web app, and should be rendered as the designers intend, in my opinion.

In the end, I think even a folder structure would be the right way for front-end as well as back-end for most websites. Here's your articles in HTML, here's your images, here's the product you can purchase as some kind of standardized json-object. Does this make sense?