Of course these transitions are probably not more than a second or two at most, but over the course of the day it all adds up. This is something that Apple is looking to change in iOS 12 with some UI tweaks. This was revealed during one of Apple’s WWDC sessions last week where users can now interact with their phone without having to wait for the UI’s animations to finish.
What does this mean? Basically while an app is going through the animations of closing when you swipe/press to go home, you can already start moving to your next task, like swiping to a different page on your home screen. Users will also be able to launch multitasking while an app is launching, which means that if you launch the wrong app you’ll be able to quickly shut it down.
That being said these actions will need to happen really fast so if you’re not particularly agile then maybe you won’t be able to take full advantage of it. However for power users who are pretty adept at using their phones should be able to appreciate these changes.