Ironically though, I'd be willing to bet that end-user performance on most traditional server-side-rendered apps using the "heavyweight" RoR framework is far better than the latest and greatest SPA approach.
In a previous life I did back office development for ecommerce. We had two applications, one RoR monolith and a "modern" JavaScript Meteor SPA. The SPA was actually developed to replace the equivalent functionality in the RoR application but we ended up killing it and sticking with what we had. Depending on what you're trying to accomplish server side rendering is just as good, if not better than the latest and greatest in client side rendering.
