Highly debatable. I've had great success developing highly dynamic websites using progressive enhancement and directive/web component like approach.
People often smirk when I mention progressive enhancement these days. But the same people often claim that something is "impossible" to do using PE, while it's not only possible, but downwright easy. This makes me think most of them never even tried this approach seriously.
My overall strategy is creating some crude "date model" of the application in pure HTML, then identifying additional behaviors I need to make it look/work the way I really want to. I implement each behavior as separate JS libraries. The libraries are configured by adding additional directives to my markup, so using and re-using them requires no coding per se.
You would be surprised how much you can accomplish this way. Moreover, it forces you to write highly reusable components that are easy to reuse.
CSS3 is a great help in this regard, because (in most cases) you do not have to specify look-and-feel of anything in the library itself. You can simply generate some additional markup that can be styled separately for every app.
