I think SSR is only important because of cargo culting. This site right now uses Sapper to render the the entry page after that, it's all Javascript. I never cared about Sapper's SSR ability. Only that it kept close enough to HTML, CSS, JS and easy to understand routing. No weird shit.
Now that I've discovered lit-html which is lightweight and helps tremendously with building web applications without a framework why bother with React, Svelte or anything else for small web apps? Web Components are easy AF. Bulid a web component with lit-html or just the CustomElements API and you can use that element anywhere with no bs. These things are high performance. No waiting for React or Svelte or whatever to load in it's libraries since it is all in the browser.
SSR does not lower your latency with regards to first byte to client. Client side rendering has higher performance with regards to first byte to client and any flash of unstyled content can be mitigated without the significant engineering efforts needed in SSR. Google will see your web components content and rank your site very high in terms of page load speed.
What's the point of SSR if it is not higher performance? Because people might be able to see content rendered by the server, but that would matter if the content was slow to render using web components. I could say people on slower connections would benefit from SSR, but if you have a light libraries for web components then what's the point if the client side can immediately show a placeholder on first load which most people will actually wait for since the screen isn't blank?
Most uses of SSR is just because of cargo culting not because it helps performance in significant way. SSR is just the cool kid on the block. Well, soon this blog will be only web components and no svelte, sapper whatever. No one will notice the difference between client and server side rendering. Google will show results as usual.