Phylosophy

React router was created by people who came from an ember background and thought of routing as something static rather than dynamic. Because of that, the early versions of react-router (up until react-router-v4), used static routing rather than dynamic routing.

Since v4, they became better react developers and rather than making a router for react, they changed their patterns to make a true react-router, a routing system that followed reacts philosophy and worked with it.

Verions 4 and 5 take advantage of things like composition and hooks.