How are you ignoring the fact that Hamas takes the fuel. The UN just said they had their fuel stolen. So those babies will die, more Israelis will die, and more Palestinians will die.
If the UN had forces guarding supplies and stopping theft, that might be different. But you are asking Israel to allow in supplies that are be and will continue to be stolen and used in attacks against Israel. Ignoring that it will not save civilians.
Because they'd be attacked, kidnapped, and/or killed. Seriously what kind of question is this? How do you propose they go into Gaza, distribute the aid, and not get attacked. Hamas is rolling right up to the aid and stealing it. Are you suggesting Israel completely occupy the region and maintain security in order to distribute aid?