What is the difference between a web page and a web application? Though we tend to identify documents with reading and applications with interaction, most web-based applications are of the blended variety: Users can consume information and perform tasks in the same place. Regardless, the way we approach building web applications usually dispenses with some of the simple virtues of the readable web.
Recently, there’s been a move towards “isomorphic” (or “universal”) applications — applications that can run the same code on the client and the server, sending prerendered HTML from the server before delegating to client-side code. This approach (possible using Express as the server and React as the rendering engine, for instance) is a huge step towards a more performant and robust web application architecture.
This little exposition amounts to no more than the notion of doing things The Web Way™ with a few loosely confederated concepts and techniques, but I think you could take it and make it something special.