Overnight I was automatically "upgraded" by Apple to iTunes 12.7 without being granted a choice if I wanted to - it just happened. The new iTunes (preparatory for iOS 11) has removed the iOS App Store and all management of apps, as well as management of Ringtones and iTunes U, from iTunes. In the long run, I actually like this because iTunes became a bloated mess. But in the short run, the iOS app store and app management are gone from iTunes on your Mac, which takes some getting used to. They are now handled on your iOS device only. The App Store in iTunes is kaput and there?s nothing you can do about it, so dry your tears and move on as quickly as you are able.
This will become a major pain in the backside only if you ever have to restore your iPhone from a backup. I had to do it twice and it took a long time. Now it will take even longer and use your bandwidth. You can still backup and restore your iPhone through iTunes but apps will now be restored only wirelessly as a re-download from the Internet. If you have data caps on your Internet plan this could be a problem and you might have to got to McDonalds or the library to restore.
If you have custom ringtones, that you did not purchase from Apple, you should make a backup copy of the Tones folder in case it disappears in a future version of iTunes. You can find it at ~/Music/iTunes/iTunes Media/Tones.
This is all the good news I can share today.