"None of that addresses the fact that we can't design buildings to
sustain any sort of impact and/or explosion."

Tom, history has demonstrated that we both can and have constructed
large buildings that have demonstrated an ability to withstand such
threats -- The problem actually is that today no one wants to pay the
cost for this quality of construction or to accept the associated open
floor space constraints/limitations.
Disasters like the WTC are in my mind the result of weak spined
structural engineers allowing real estate firms to dictate building
design and priorities that, in this case, focused on unobstructed, open
floor space, uniform building cross section, and the use of
inexpensive, balloon style construction with its implicit domino
failure mode.

Had the buildings not been destroyed by terrorist jets, given enough
time an office fire on any one of the upper floors would eventually
have led to an identical outcome (but hopefully with fewer lives lost).
WTC is, sadly, just another engineering disaster to add to the list.

Note that in spite of many fires, airplane collisions, and bombs, all
of the great skyscrapers built prior to 1950 are still standing. It is
interesting to note that virtually none of these represent a uniform
building cross section nor shell supported, balloon construction
technology. Evidently buildings of this calibre are simply too time
consuming and costly to construct today, or simply that insurance is
cheaper than quality engineering and construction.

Just my thoughts on the subject.

Kindest regards, Harry C.