Why do we need Redux?

So, why exactly do we need Redux in our application development? I mean, we've been getting by without it for a while now. Is it really necessary? What kind of problems does it solve that we couldn't solve with just plain old JavaScript or React's own state management? And isn't it just adding an extra layer of complexity that we don't really need? Can you help me understand the benefits of Redux and why it's worth the investment of time and effort to implement it in our projects?