Hello, yes,
removal of apple app store from iTunes helped to streamline the app and keep it more focused on its main business but, on the other hand, we users can no longer store and update iOS apps on one computer to then sync on our multiple mobile devices, saving us huge bandwidth in any place it is a premium or we are charged by usage.
Another feature we had lost, is the ability to install/remove apps that have been removed from store (for any reason) but we had purchased and were still working good and, with the new way of sync, these apps will be lost forever.
The only options you have right now, are:
1) downgrade to latest 12.6 iTunes, but this will works until the app store still sync with it, and we don't know how much this will last, or
2) let Apple recognize they removed a feature without giving us any equivalent alternatives (see feedback link in other answers), and no, make app sync directly from our devices is not an option, see the bandwidth issues above mentioned. Just hope Apple will put that feature again as it was, in the appropriate place, that is not iTunes but maybe the Configurator app. Or even make one ad hoc app for it.
or else, when iOS app store will stop working with iTunes 12.6, you will be out of luck.