Which technical functionality that you were actually using in earlier iOS releases is gone with iOS 11 or earlier with iOS 10? Which features that you actually use you expect to be gone soon?
Here is my list:
1 Applications' access to the routing tables - lost in iOS 10
2 The ability to display cellular signal strength in dBm using Field Test app trick - lost in iOS 11
3 Applications' access to the ARP table - lost in iOS 11
4 The control center shortcuts to really switch Bluetooth and WiFi off
5 (pending) AirPort utility to be gone anytime soon as there will be no more new AirPort APs, the last true WiFi scanner/analyzer for iOS to be gone with it (third party apps lost direct access to WiFi controls and data ages ago)
Here is my list:
1 Applications' access to the routing tables - lost in iOS 10
2 The ability to display cellular signal strength in dBm using Field Test app trick - lost in iOS 11
3 Applications' access to the ARP table - lost in iOS 11
4 The control center shortcuts to really switch Bluetooth and WiFi off
5 (pending) AirPort utility to be gone anytime soon as there will be no more new AirPort APs, the last true WiFi scanner/analyzer for iOS to be gone with it (third party apps lost direct access to WiFi controls and data ages ago)