For a very long time, the people of Europe looked around and what they had and could build and said "Rome was nicer. Rome's ruins still look a lot better than what we have." For 1000 years at least, it was like that. The small principalities and territories that existed also seemed insignificant to an Empire that stretched from England to Iraq. Rome had a population of over a million people at its height; something the other cities didn't begin to reach until around 1800.
Before the start of the industrial revolution, there was still a general sense that "Rome was still better and nicer, and with better water and engineering and construction"
Europe could build awesome cathedrals. Look at Notre Dame. But it took 100 years to build it in the 1200s. Look at St Peter's - but that took 120 years to build in the 1500s.
The Basilica of Maxentius and Constantine in Rome, built in 308 AD, took 4 years. The Coliseum took 10 years. Nobody built anything like it until around the 1870s.