Most of what ATC does is routine. New airplane arrives in their airspace and calls ATC. ATC sends the first step of the standard arrival route and any known issues with the flying condition reported by other aircraft. Then it's time for a turn and descent in the route. ATC radios them direction and altitude. Repeat this half a dozen times. The plane might be flying a bit fast. ATC tweaks the route slightly to give them more air miles and tells them to slow down. Now the plane is at the initial approach fix and it'll join and follow ILS all the way down to the ground, with the ATC giving altitude clearances and eventually the landing clearance.
Frankly most of that can be done automatically, and in some cases better. The computer won't forget to give a descent clearance, it'll speak clearly at all times, it can talk to 2 planes at the same time, it can project flight paths way more accurately. ATC only needs to step in when something unusual happens, and even then there can be pre-programmed processes that can happen much faster with computer support, e.g. telling all planes to enter into a holding pattern at non-conflicting altitudes or telling them to all go to their alternates.