Please demonstrate one instance in Scripture, Tradition or the Magisterium prior to Vatican II in which the Church has ever taught an "existential" understanding of Hell. Jesus taught that Hell was a place of fire. Do you think that you know more about the subject than He did?
Jesus frequently teaches in language that's prophetic, which is to say, not literal, but conveying truths distant and hidden that are not apprehensible to the human mind. The everlasting fire of hell is the fire of utter destruction; the fire of the burning bush is a prophecy of the Resurrection.
Do you think that you know more about the subject than He did?
No indeed. Do you think you know more about how to interpret revelation than Vatican II?