Calling this argument a strawman is pretty dismissive and is not a technical arugment. There are lots of client side interactions that do not need to be blocked on data from the server. Popup menus, modals, collapsible lists, rich text editing etc.
Also think about what actually has to happen when you interact with a server rendered app vs a client rendered app. Once the client app is booted you don't have to pay network latency, html parsing, FOUC etc on every interaction as you would with a server rendered app.
Also think about what actually has to happen when you interact with a server rendered app vs a client rendered app. Once the client app is booted you don't have to pay network latency, html parsing, FOUC etc on every interaction as you would with a server rendered app.