In the apps that I've built, having many components manage their own private state makes it hard to coordinate said components, because all of the application state is stuffed inside different jars that you can't easily peak into.

It's been much easier to pull all app state into a central, db like structure, and allow components to connect and query that structure for whatever data they need. It makes making changes to components in the future easier, because all of my data is normalized in a structure, and it's all possibly available to any component in the app.

I've found that with MVC, if you design the private state a certain way, and in the future need largeish independent components to coordinate, well, you're going to have a bad time.

So redux or not, I'm definitely a fan managing state as it's own separate thing, and having components able to query and connect to that data structure, without having to pipe props down a tree of components, which leads to an app that's hard to change.