How would you implement Google Maps as a SSR app? -- same question for ArcGIS, Figma, an arcade game, or a Zoom clone. It's a serious question -- do you think that would be possible for any of those?
I contend that to build a coherent, usable web app of any of those types, there has to be a lot of client-side scripting. Hence, a SPA is the best architectural pattern.
Sure, you could use SSR for the layout of the page... but in that case, why not skip HTML rendering altogether by shipping raw HTML/CSS for the app's layout? Then you'd only need JS to power the contents of <div>s where the app's functionality is located.
