Maxwell didn't discover Maxwell's equations. He came up with an addition to Ampère's Law that effectively completed the Theory of Classical Electro Dynamics after around a 100 year of theorizing.

If we go back in time and look at Euclid who lived around 300 bc. It was his works, that represent the culmination of several millennia of Geometry that got passed down to us from Antiquity that we attribute the discoveries of Euclidian Geometry aka Plane Geometry (i.e. the one that you use in everyday life). This makes him a very good analog for a Maxwell of the Past.

Euclid was active in the Reign of Ptolemy the First, during the wars of the Diadochi, or the Wars of Succession after the Death of Alexander the Great. When you read books about the Hellenistic Era, you hear how Alexandria was a city of Culture and Learning, and the great strides made by Hellenistic Artists, Poets and Engineers but nothing about how Plane Geometry was formally standardized.

Back to Maxwell. His equation by themselves don't make up a complete theory. They are part of a larger Electroweak Theory, which in turn is probably part of a larger Grand Unified Theory (everything but Gravity) and the final Theory of Everything. Electrodynamics it's self is really only a special case of Quantum Mechanics. We are already moving from one paradigm to another, replacing electrical wires with with optical (quantum) and quantum effects will soon start dominating out computations, in both quantum computing and manufacturing techniques to get the transistors that small. This puts Maxwell not as a founder, or a finisher, but merely a contributor to our greater scientific understanding.

If we take the Hellenistic Era as an example of how the history of the the 19th and 20th centuries will be written, It would expect to see political, cultural, and social history, focusing on the impacts of these scientific discoveries. The US Civil War, is a necessary set piece for a lot of what happened in the 20th Century. While Maxwell's equations underpin a lot of the technological changes in the 20th Century, the focus will be more on the impact of mass media, and the internet.

This is something that I find difficult to answer (I am actually a scientist)...

The challenge behind making this kind of claim is that scientific development is essential, but it is not often recognised. To my mind, and I may be wrong (and get shouted down by the Mods), history is a study of people and their culture and how they have changed our world... Which is why people are so fascinated by events that changed our culture or the world, such as the world wars, the US civil war, the atomic bombings of Hiroshima and Nagasaki etc.

When you look at the history of science, you see the results of scientists/engineers/inventors who have changed our culture, such as Eddison and Tesla who brought advances in electricity and the light bulb, or Einstein and Fermi who brought advances in nuclear warfare... Very few people outside of science would be aware of Erwin Schrodinger and Werner Heisenburg who had changed our understanding of the structure of the atom.

I personally feel that Feynman's approach is science-centric and extremely biased and neglects that culture and society are drivers of history. However, I also believe that he is correct. Without scientific advances which allow us to interact with each other in new and exciting ways, our culture and society will "stagnate' (more likely slow down to the point where people think that). Feynman has glossed over the symbiotic relationship between science, technology and society, making his statement untrue to my mind.