I disagree. CSS animations work very well and offer better performance. You can maintain the animation lifecycle by the React lifecycle callbacks and use of setTimeout

CSS animations do not work when you need to morph distinct components in complex coordinated manner. They are significantly slower then velocity js. Doing things available with quality solutions such as Ember liquid-fire are simply not possible.

Animations work really well with React!

The Animated library (originally from React Native) gives you some pretty basic but powerful primitives to build whatever animation you need.

On route transition you want to animate morphing unrelated components between before transition components and after transition components. You will not be able to do this in functional manner. You will not be able to do this with CSS animations. Example of how this is done with Ember liquid fire. https://www.youtube.com/watch?v=vq_BcIFM8Rc