Great Nation Who Live In the Past

This year a group of Iranians celebrated the Persian new year (Nowrouz) in Pasargad were Cyrus the great is buried.
There is a nostalgic tendency among Persians/Iranians to look back to their nation’s prosperous past, 2500 years ago. The era when Persian Empire was the greatest power in the world and possessed a rich culture. For example, Cyrus Cylinder is considered the first human rights charter in history; Persepolis was built with paid labor,...
The question is:
Why are we trying so hard to prove to the world that we had a rich culture thousands of years ago?What will the world think about us? That we have lost such power, culture and even dignity permanently from 2500 years ago up to now?
Past is gone. Let’s live in present and try building the future.