New scientific models tend to look very much like the older models in some relevant limit, even when they are fundamentally very different. Einstein's relativity looks a whole lot like Newton's relativity at low speeds. Large collections of quantum-mechanical particles tend to behave classically. This is not an accident of history—the old models worked in some domain, which is why they became accepted models. I will counter your Pratchett quote with one from Asimov:

"When people thought the earth was flat, they were wrong. When people thought the earth was spherical, they were wrong. But if you think that thinking the earth is spherical is just as wrong as thinking the earth is flat, then your view is wronger than both of them put together."