Do you know that network engineers probably spend 60-80% of their time just doing things like creating and maintaining VLANs, switchports, and routing on their networks? ACI can actually take care of this pain point and free up network and system engineers to do less mundane tasks.
For example, while you can configure things like BGP and EIGRP to communicate with the network outside the ACI fabric, it's not necessary to configure it inside the network. The spines know where every end point is and send traffic to the appropriate destination in just two hops every time.
There's also no more need to type something like "switchport mode trunk" a million times or configure scripts which you need to update everytime you use it. In fact you don't need ot conifgure modes at all in ACI. That is all handled automatically. We actually don't care too much about which VLANs are connected to which ports because everything is handled through the use of End Point Groups. Even vPC configuration consists of many less steps than it does in traditional networking.