We could build it today. What’s amazing is the resources needed to do so. People, food, time, ….
The same with other sites.
So being able to muster resources proves they are the work of an advanced pre-historic civilization or the work of aliens.
BTW, please let me know when you find a modern crane capable of lifting 750 tons of stones like those in Baalbek:
https://www.atlasobscura.com/places/baalbek-trilithon