There's no denying performance has taken a severe beating since iOS 8, and even more so with iOS 9. Dynamic blurs are extremely taxing on processors. And I don't just mean phone processors. Microsoft removed almost all of their AeroBlur UI on their update to windows 8, and say what you will about W8, it was tremendously faster. There's definitely something they can choose to do instead, and make it all look better too, right? Off the top of my head, increasing shadows while decreasing opacity makes for quite a pleasant effect. The fundamental reason for general sluggishness with iOS 8+(apart from full disk encryption) is these gaussian blurs. Eg. Spotlight lag, Control Center, iOS 9 app switcher, folders, notification center, safari on iPad... For those designers out there, what else could be an alternative? Good day!