And since you don't want a 2000 character URL, you're either storing half of the session on the server or having to build an abstraction with local storage. And since our frameworks didn't evolve to handle that, what is the purpose?
The key insight into the SPA is that you are writing a coherent client experience. No SSR framework figured out how to do this because they thought about pages rather than experiences.
Let me be clear: I am speaking about web applications. If you're providing information and only have a small number of customer interactions, an SSR is superior. CNN should not be an SPA.