[AgentME]

React is a great way to do progressive enhancement: you can have the same component code run on the server and client. On the server, it will only be used for creating static html. On the client, the component code will bind to the already generated HTML and allow client-side interactivity.

Writing rich UIs with progressive enhancement without this benefit was over-complicated pain before React. All of your UI code would either be based around binding to static HTML generated by the server or be based on locally-generated elements; if you ever had a widget that had been generated by the server that you now want to generate client-side in some context, or vice-versa, then you had to have multiple separate code paths on the client for that in addition to the separate server-side code for the widget. Having the component's code defined once in a way that works for all three contexts (client-side generation, server-side generation, client-side binding to server-generated HTML) is great.

I think people assume that because React is a newer way of doing things that it doesn't work well at the old goals (progressive enhancement) but the opposite is true!