There are few things that annoy me more than an app with unneeded transition animations between menus. An example of this would be the Xbox app on Android. Whenever you navigate to a new menu, it always has a stupid slow fade-in animation. Why do we need an animation every time we switch between menus?! It adds that much more time before we can actually use that section of the app, just because we need to wait for this stupid unneeded animation to run. It's like whoever wrote the app was browsing a generic animation library and discovered the fade-in animation, and thought to themselves "Woah this is so cool, it'll make the app go whooooooosh every time they change menus, they're gonna be so impressed!!"