To be clear, even the twin towers' building engineers and designers never claimed that a modern 747 wouldnt be able to bring them down. IIRC, one of the engineers said they had taken into account a smaller plane, like a 707 or DC10, but they did not think it would be cost effective to build against such a scenario as the jet would be so large and carry so much fuel it probably would not have been possible.
TBH, I don't think ANY modern building, even ones put up in the last few years, would be able to withstand a direct strike from a fully-fueled 747; the plane's force and speed is too great, and the fuel carry is immense.