Even with dirt-cheap CDNs it seems like the respectable thing to do.
Especially for mobile devices. No CDN will solve poor last-mile connectivity, or save users data.
The main trap people fall into, in my experience, is thinking of it as "HTTP cache++", and just applying it to unstructured sites.
If you want a quality offline-first experience, you need to approach your product, from the get go, as an application. (Which just happens to be written with web technologies).
It is tremendously easier to add SSR to an offline-first, well-structured application using best practices than it is to make even a subset of your SSR-first application provide a usable offline experience.
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