That was one of the biggest tragedies in recorded history. Do you even know what it did to the economy? It was like Black Monday on a 5x multiplier.
The World Trade Center, keyword TRADE. This isn't pokemon shit, this is real-world stocks and dollars. The portfolios were ruined.
The next time you laugh at that, think about the human beings that had their vacation bonuses decimated that day. Think about how the economic blow made countries like China catch up to us. Just think about that.
Another thing to consider - The WTC gets emphasized to the point where the other targets are rarely discussed. The 9/11 attacks were an attempted de-capitation strike on the US military and government. One plane hit the Pentagon, but did relatively little damage due to the Pentagon's nuke-resistant design. Another plane was heading to the white house in the passengers attacked the hijackers and forced the plane down in Pennsylvania. The WTC was a symbolic target. The military goal was to either kill the POTUS or severely damage the white house, and to destroy or severely disrupt the Pentagon. The WTC ended up being far and away the most dramatic part of the attacks when the towers unexpectedly collapsed, but there was much more too the attacks than the WTC.