I agree with the quote about not making Redux your first choice on simpler apps, but would add that MobX is a great alternative that's lean & simple enough to add to even the smallest apps. Redux can definitely feel heavy for small apps & rapid prototypes. MobX is very easy to set up and include even if you only end up needing it a handful of times.
The reality is that even in the simplest apps, you're going to end up with a few shared states. Without using any Flux tools, you'll eventually resort to using Context (which is messy and hard to maintain), or storing app state at the component level (and needing to refactor later).
Eventually even the simplest apps will also have some sort of app logic as well. Architecturally speaking, it's a lot cleaner to be able to put that at the top level instead of burying it in your view components. When you go in later to make updates you'll know right where to look!