Why, according to Winston, did tragedy now belong to an "ancient time," no longer being possible in the present?

According to Winston, the main character in 1984, tragedy now belongs to an "ancient time" and is no longer possible because 1984's society is no longer capable of feeling any emotion as a consequence of the Big Brother's actions.

That ancient time, before the Big Brother, George Orwell explained was "a time when there were still privacy, love, and friendship, and when the members of a family stood by one another without needing to know the reason."

Among other things, Big Brother burnt all the books so that people have no more access to the emotions conveyed through books, like the emotions Winston is capable of feeling as a consequence of reading books written by Shakespeare.