But let's be realistic.
The Twin Towers' design did damn good at protecting people. Roughly 2,500 people died in NYC on 9/11 after buildings which held over 50,000 people crashed down. That's about 5% of the potential occupants. Of that 2,500, almost 500 were rescue workers which were rushing into the damaged buildings and then around 200 more which were on the aircraft that hit the buildings. How many of the 1,800 remaining victims were incinerated within seconds of the planes hitting by burning jet fuel? I would say at least 500-800.
Do the math, and you will see that those towers did a fantastic job of saving lives considering the circumstances.