For example, the places the Romans conquered where never really the same, whereas the culture of the people the Mongols conquered stayed pretty much the same, though some were inriched (like Mongolia), while others were lessened (like Persia and Russia, though later leaders made up for the original burning of mosques and churches).
But then by your own logic Rome made up for say the conquest of Gaul by later building roads, establishing secure boarders, the Pax ROmana, etc.