You should have a look at MithrilJs, it's smaller and faster than React, functional, composable, a small API so small learning curve. XHR and a router are already included when React is only a viewer plus you can write your code in ES5, no need for Babel, JSX etc...
It is being used by big Companies (Nike, Vimeo, Autodesk) and some very high traffic website (Lichess).
Personally I have a React fatigue, overwhelmed by FB marketing.
Even Hyperapp seems more interesting.
This post was about tools used in the build process of Web apps. You can use these tools with React, Mithril and Hyperapp projects.