So little discussion... Do people take progressive enhancement for granted, or is it that it isn't well-respected anymore?
It’s largely not respected anymore. If you are building a React app it’s not really like a webpage. It’s more like an app. JavaScript and a modern browser are expected, and most users are going to have them. However, if you are building a site that needs to be indexed and searchable by Google, you should be taking progressive enhancement into consideration if only for SEO.