That's not true. The idea that the web should gracefully degrade and continue to display content in browsers of all types has been live for... the entire existence of the web.
There is a new trend to expect all clients to run js, yes, but that is a bad assumption.
I understand that is an ideal, but "browsers of all types" is utterly unrealistic, and hasn't been the case in the wild since the 90's.
Not only does the modern web expect you to be running JS, you're expected to be running a browser that's at most 1 version off the most recently released version. Supporting only evergreen browsers might just be the best thing that's happened in web development.
Graceful degradation was a thing for a very brief period in the lifetime of the web, and hardly anyone actually had the resources or inclination to even pretend to attempt it.
We got conned into this shitty world where HTML shovels ajax and giant JS payloads.
Old web was information and a theme could be written locally and applied to everything.
New web is almost as trashy as the App Store.
edit: my imagination is vivid, and it doesn't end at React and the iPhone. We can do so much better. Semantic information markup without ads and presentation details. Shared p2p, unsiloed. Completely free.
There is a new trend to expect all clients to run js, yes, but that is a bad assumption.