The other thing is, both towers were plane impact resistant. Both of them took dead square hits from airliners and remained resolutely standing afterwards. What it turned out they were not proof against was an ongoing raging inferno inside that was hot enough and carried on long enough to weaken their critical structural elements.

If the planes had not been laden with fuel and/or if it had not ignited for whatever reason, the towers probably would not have collapsed. They probably wouldn't have been readily repairable, though, so then the question would be what to do with two massive skyscrapers with giant holes in the middle of them. They'd probably have to be demolished eventually anyway. Said demolition would have killed far fewer people.