Those floors had two sets of 1/4" rebar grid in them and there were a number of trusses involved. Of course there would have been local buckling failures, but it would probably not have buckled the entire length of the floor. The real issue is what damage going through the length of the floor does to the plane. The plane would have been hitting the floor edge on, not just diving down through the thickness. It would have had to plow through the length of the concrete with two sets of light rebar in it and trusses with buried knuckles in the concrete. That would appear to have done much more reduction to the momentum than diving through the floor.
Yet in all this inner structure and floor space, there would have been explosive charges set for the controlled demolition which didn't go off and didn't set the whole thing when the plane plowed through it.
How do you explain that?
How can you possibly argue about how the plane got through the building and not think of the controlled demolition charges which are supposed to be there, waiting to be ignited?
After all, you do suggest controlled demolition in your username. How does one rationalize such a paradox?