The original poster wrote, "Why do we practice throwing if aikido is an art of balance?". He goes on to say, "Kuzushi is clearly not the right word ..."
Seems to me he must be talking about something else, certainly not kuzushi.
Aikido is not the art of balance. What we do is, literally, The Way of Aiki. It is aiki that we must seek and develop. The main aim is not harmony, the way of harmony, the way of peace, loving your neighbour - none of that hairy fairy stuff (they play a minor role). The main aim, in my opinion, should be The Way of Aiki. Kuzushi is just one principle we find along the Way, and it's a pretty important one if you ask me becuase not until you take uke's balance can you actually do anything to them (in Aikido).