They had stuff like theatres, temples, and aqueducts that still stood after being utterly neglected for a millenium, whilst their fancy new churches took centuries to get built and needed constant maintenance. It’s easy to see how this would seem wonderful, or how they would take ancient Rome’s engineers and architects as models.

Also, we tend to take things we’re familiar with for granted, and overlook them when comparing different societies. So of course, ancient civilisations were terrible for other reasons, but still...