The circular terminals made sense when it was built, right before the era of security checkpoints. It was obsolete very quickly, and it sucks to use b/c essentially every 2 or so gates has its own security checkpoint. You get corralled into a little waiting area and if you want to leave to use the restroom or eat or whatever, you have to leave the secured areas and then go back through security to get to your gate again. The security lines get backed up when everyone shows up at once to go through them and will back out into the concourse because there are only 1 or 2 scanners per gate area. The gate seating can be crowded. If you connect there, you have to go through security unless you luck out and your connection is at the other gate in the same secured area.
But before security theater it was great. You parked close to your gate and walked right in. It needed a replacement/overhaul badly for the current era.
I will say this, the time I flew out/in of MCI it was clean and seemed well run despite the obvious drawbacks of its design. Another nice thing was if someone was meeting you to pick you up or see you off, they could stand in the concourse right next to the gate (there is a glass partition between them).