App Library

What exactly do you want un-done?

The App Library is an additional way of seeing your Apps, it's a now standard feature. Nothing to un-do. It does not affect your app organization in your other home screens.

It automatically organizes the apps in groups by the category set by their developers.

click here ➜ Find your apps in App Library on iPhone - Apple Support

As I said, the App Library automatically arranges them in groups by category. This cannot be changed in any way.

This does not affect your other home screens in at all, and your apps will continue to exist there in which ever order and arrangement you have them.

Its simply an additional way of seeing your Apps, but you cannot change they way it displays them there.

You can simply not swipe all the way to the end and ignore them if this is somehow irritating to you.

App Library is a feature of iOS.

Its been there since iOS 14. almost 3 years ago.

Not sure what you think happened. If you recently updated from iOS 13 or earlier then it may be a new feature for you.

Nothing has changed about it since it was made available in 2020. App Library since its introduction has always worked this way.

You can tap on the search bar at the top of the App Library to see an alphabetical list if that is what you were seeing before. The way it displays apps there has not changed since it was introduced in 2020.