As for why the company has chosen to refresh Google Translate first is unclear, as there are many other apps that are used daily by a much larger number of iPhone owners.
As it is with other Material You updates, the buttons and basically everything that you can tap on now takes more of the screen real estate, making it easier for the user to navigate the UI. This also makes the overall look of the app arguably cleaner and more simple to look at.
Here is how the app used to look before Google released the server-side update to introduce Material You:
All of the functionalities have been kept, as you can see. The main difference is in the app’s focus, which is now placed more heavily on input. It is easier to initiate a translation via voice, typing, or handwriting after tapping on the pen icon. The shrift is bigger and much more readable than before too.
Of course, this being a Google application on an iOS device, there are some features missing that are present on the Android version. One of them is the ability to long-press on languages to swap languages. You also cannot swipe down on while in the main screen.
One last small note is that while on the Android version of Google Translate the app adapts the color for accents to the wallpaper the phone is using, here it just defaults to blue. None of these missing functionalities, however, are too significant for the end user experience.
