One might debate if a page really needs hundreds of kb of js to function, but then again, this is not much different than the classical progressive enhancement site with jquery etc. layered on and reacts server rendering can make to page easily available and working when js is disabled.
Careful planning is required of all frameworks to make a JS free version. I wouldn't say it's a feature of React or that it's free.
> One might debate if a page really needs hundreds of kb of js to function, but then again, this is not much different than the classical progressive enhancement site with jquery
JQuery was a crutch that wasn't strictly necessary and with modern browsers you can largely do without it and write pure JavaScript. Assuming you know how, which I would wager most developers don't.
It really isn't that hard to design a functional HTML site and then layer Javascript and AJAX over top of it to enhance the experience. There are very few sites that actually need to be using Frameworks like Angular and React.
Sometimes I wonder if most developers would even be able to design a functional site using only HTML. It seems like most don't know the difference between a button and an anchor.
With modern server side frameworks it's even easier to support graceful degradation or progressive enhancement as the frameworks will handle the accept header processing for you.