One of the non-intuitive changes Apple made to iOS 11 is how you uninstall or delete an app from the device. In prior versions you tap and hold the app icon and then tap the X circle that appears to delete the app, but this does not happen in iOS 11.
Apple has set up iOS to automatically offload apps that you do not frequently use, but I haven't seen any info on the criteria it uses to make such a decision. Even though iOS will delete an app, the app settings and data will stay on the device so if you reinstall it, you can pick up right where you left off. iOS 11 calls this Offloading an App.
To delete an app you tap Settings, General, iPad Storage, tap the name of the app you want to delete and then tap Delete App.
While I get that when you delete an app you really are managing storage, I do not think this is an intuitive place to look to delete an app. After trying to delete an app the old way, my next step was to tap Settings, then scroll through the list of apps, tap it, expecting to find Delete, but instead all you see are all other application specific settings OTHER THAN delete.
Frankly, having the OS take over control over something this as Apple appears to intend happening is very much a Microsoft way of doing things, which is not very user friendly in my opinion.