True, not only Roman and Greeks, the same thing happened with Mughal Empire.
Immorality comes when a nation/empire thinks that there is no economic or military related threat to them.
When you are not battling others, your battle with your "self/ Nafs (نَفْس)" starts.
This concept is foreign to westerners but we Muslims know its importance.
They think we dont understand what is going on.
The worf Nafs, was mentioned 298 times in Quran and highlights the importance of controlling it:
Wikipedia
Link
Even if we dont make it about religion, the current mental health crises show us that people are not at peace with themselves.
But here, we know that it is fundamental to surrender your "will", control your Nafs, only then you will be at peace.
One of the links I shared above says that "You have no right to happiness".
And the science agree with this:
A growing body of research shows that the pursuit of happiness actually makes us miserable.
Link