Earlier quoted context omitted.
"what about empires that actually survived or adapted" — which ones exactly? Empires are pathological developments of nations. They don't tend to survive all that long.
Didn't the Roman Empire last nearly 1,500 years in one form or another?
And the Byzantine Empire shrunk greatly after the first few hundred years. Most of its life it was more like a Greek nation that sometimes managed to expand to control parts of the old empire.