I don't think anybody would argue that server-side rendering could deliver any or all experiences. Clearly even gaming is possible with a thin client (https://parsecgaming.com/).

What you lose at that point is latency. A round-trip to even the closest CDN is going to be vastly slower than rendering the next frame on a GPU with direct access to write to your screen.

It's not that things are impossible server-side. It's that clearly server-side rendering is not the universal answer for more-performant applications.