Interesting, as that's very much how my mental model of how Rails works:

1. The routing layer is all about declaring a resource which gives you all 7 major REST operations, and

2. there's a nice facility for responding_to any data format (html, json, js, text, etc) you want.

With rails scaffolding, you can pretty much get all boilerplate code written for you, and have it very simply implement a REST backend for a more "heavyweight" javascript framework (angular, ember, etc).

I wonder if the issue is that rails didn't originally start out this way, and now people assume that Rails is stuck in the past?

I think the article gets it right in that Ruby needs better concurrency primitives (promises are a nice idea), and esp better performance. If Javascript can be as fast as it is with V8, there should be nothing stopping Ruby from achieving similar levels of performance.