The complexity is mostly from people approaching it from a confusing direction. Some of the naming is confusing ("action", but actually it's an event or message, is the worst one). Somehow everyone comes away from the tutorials and docs thinking that the typical code structure used in them has to be how you do it (see many of the complaints on this very page) as if it's much more a framework than a library.

I had a similar experience with it coming in to a recently-started React Native project at work, having not seen React, React Native, or Redux before. At first I was fairly confused (see: awful terminology, painful example code which everyone seems to take as gospel and which had, in fact, invaded our codebase).

Then I started to get an inkling that I was being tricked. I looked closer and... it's two event dispatchers. One of which it's mostly up to you to implement (the reducer). Plus a really short list of suggestions for how to write the code (mainly: don't screw with state in certain places/ways). That's it.

It's paper thin and dead simple, but somehow most people come away from the tutorials and docs hopelessly confused. I think there's something deeply and perhaps irredeemably wrong with the docs/tutorials and with the way Redux's proselytizers communicate. I can't figure out how else they could manage to confuse so many people about such a simple thing.