There's theoretically some performance benefit to rendering client side over ajax because the pages can be trivially cached, though you then run into the issue of pages being placeholders for a moment while the subsequent request(s!) run. Hence the UX anti-pattern of skeleton screens.
I don’t care for skeleton screens much in any case, but there’s no reason why skeleton screens couldn’t be limited to client-side page loads while the client waits for the data. The server could and should still fetch all the data and send down a fully-rendered page.
