These were all strong civilizations, yes. Then again, building underground canals carved out of rock is a lot harder than building a basic water system would be today.
Also, large civilisations were the first political tool that allowed to make peasants work at digging rocks 40 kms from home rather than goofing off in one's field during lower times of agricultural activity. And that's actually quite hard to achieve. Un roi sans divertissement est un homme plein de misères
