There are no humans left to consider the event a "tragedy"
If humans went extinct there would be nobody left alive for it to mean anything to. The universe does not have a point of view. It was neither better nor worse off during the ice age as it is now.
Other creatures do not care whether or not we are here and if they do, they are unable to express this sentiment. Tragedy is a human concept. Without humans, tragedy does not exist. Therefore, human extinction would not be a tragedy. It would be utterly meaningless as there would be no one left for it to have meaning to.
Even though the world can’t express an opinion, there are practices and activities we do that are inherently “good” or “beneficial” to the world. It would be a loss to the universe if these practices were to disappear. Other animals also have interests. Whether or not we would call that a view is debatable, but our extinction would impact and have meaning to other animals. Therefore, it is possible to weight up if this impact would be a “good” thing or whether it would be a “bad” thing and our extinction could even be considered a tragedy.
P1: Tragedy is a human construct. P2: Without humans there is no tragedy. P3: Therefore, human extinction would not be a tragedy. It would have no meaning to anyone.
P1: Tragedy is a human construct but positive and negative impacts are not. If the loss of humankind would have an objectively “negative” impact on the world, we should consider this a tragedy. Therefore, it would not be meaningless.