"Server-side rendering is not a fallback; client-side rendering is an enhancement."
I would further and say client-side rendering can be (not "is"), a performance optimization for subsequent page loads (and offline). It's only a net-win if you invest non-trivial effort (SW, streams, race network, handle long-lived tabs and cache misses to old JS, etc).
In almost all other cases, it merely produces a slower, less usable, less available version of itself.
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