I'm not quite sure what exactly you're asking here. Are you trying to say "I've seen apps that are slow, and they use React+Redux, therefore using React+Redux makes an app slow" ? Because if so, that doesn't make sense logically.
Writing apps with React+Redux (or any other client-side framework) doesn't automatically make an app slow. They're tools, and it's your job as a developer to use those tools appropriately.
Writing apps with React+Redux (or any other client-side framework) doesn't automatically make an app slow. They're tools, and it's your job as a developer to use those tools appropriately.