Earlier quoted context omitted.
The whole idea of a "site" full of "pages" doesn't really suit a lot of modern use cases. What do you do when your "app" isn't really a "site" to begin with? Like most of the apps in Google Workspace, or Maps, Earth, etc. It's not their URL structure that gives them value, but the buttload of realtime clientside interactivity enabled by JS. How are you supposed to "less JS" your way out of that?
Applications like you’re describing should consider less DOM and more Canvas API. The apps aren’t documents. They’re more like video games. DOM manipulation and rendering usually degrades performance more than the JavaScript. One essay on this topic… https://medium.com/young-coder/the-future-web-will-canvas-re...
Games and maps are just an extreme version of that, but other examples where clientside DOM apps with heavy JS can still be faster (compared to old school server-side HTML) and easier to work with (compared to canvas) are email, e-commerce, ebooks, dashboards, chat, forums, video tubes, search and filtering, galleries, documentation, project management, etc.