IMO we would need 2 split the document part from the application part. Have a set of elements and a document format just for blogs and news websites , and more complex components and APIs for application websites. Then you could have a browser that would be more simple that will be enough to browse blogs,forums and news sites and a more complex browser for SPA applications.
We have to admit that rich web application can be very usefull, even during Java or Flash days we known that sometimes you need an animation or a simulation on a page to better present some content.
Though it makes you think if we had an 100% open source Flash, then you could have used it for complex SPA like Figma while keeping all the bloat into an optional plugin , if the plugin was optional developers would not be tempted to use it unless is needed and it it was needed they would have use something like Flex (a Flash GUI tookit) and not reinvent the wheel constantly.