In my experience if the application state is overly complex then that is a result of the design, and that usually leads to a bad experience for the user.

Though it is possible to overengineer this, you're probably underestimating ho seemingly simple apps can justifiably have complex state.

Say you make API calls. Your application state just grew to reflect

1. Pending request 2. Request succesful or failed 3. Request result or error 4. Finished request.

Redux apps track all of this explicitly. The alternative to this is not reducing statefulness. It's just ignoring it with all the brings.