The problem with the SPA is that the browser is a document platform being abused to run GUI applications. It's missing the core primitives that real UI platforms had in the 90s, like decent smart sortable tables and data bindings. So all that crap is redone in JS ten thousand times by developers of varying talents and the result is, has been, and will continue to be crap usability and hugely bloated sites.

It's time to replace the HTML part of the browser with something else designed for purpose: making rich UIs that use platform-native widgets and mirror the human user interface design guide for the platform. XUL was a step in the right direction.