I don't understand why people can even think about complaining that their iPhone or iPad has become slower after an update. Of course it does that, over time. Especially since iOS 7, everything has gotten more advanced than ever before. All-new design, a lot features.. That just costs some performance. You can't expect an old device to run all of that without a problem. Also, it's still your own choice. I've had an iPhone 4 running on iOS 7, and an iPhone 4s running on iOS 8 and 9. Did I complain? Hell no! Why? Because I realized that this old hardware isn't capable of running the many new features well enough.
It's a total difference story when speaking about the latest devices like the 6s (Plus) and 6 (Plus). If they would be unusable, I'd understand this. Maybe even with the 5s. But please, the 4s is now around 4,5 years old. Once iOS 10 is out, it will be 5 years. You should be happy for having so many updates for such a long time. When you go Android, you'd be in the update train for less than two years.
I'm sorry, but this case is as ridiculous as the many other cases in the U.S. these days. Heck, in the Netherlands they would laugh at you if you'd come up with this sort of cases. It's plain stupid, sorry.