Even without identifying the hallmarks of an interstellar visitor, the so-called evidence of alien intervention is only impressive when analyzed under the scope of lean systems manufacturing. There is not a single ancient wonder of the world that couldn't easily be replicated with basic tools, simple machines, massive workforces, and lots of time.

Basic tools and simple machines: everyone has some concept of the stone age and can understand a demonstration that long, straight, round wood = wheel && wheel = massive work potential.

Massive workforces: put a child in a room with blocks, what do they do? Try to figure out how tall they can stack the blocks. Have multiple children? Eventually, they figure out that working together can create more robust towers. Humans like to build up. Put sand castle tools on a beach? Children and adults aggregate to build the most impressive structure and moat. It's human nature. When there's little else to do, people like to see if they can make big get bigger. The native workforces build themselves, and where gaps exist in teams, there's always slavery in the banana stand.

Lots of time: each pyramid of Giza took around 20-30 years to create. Compared to all of recorded history, that's nothing, but compare it to NYC skyscrapers. The Empire State Building took just over 1 year to build; if people were told that it would take 10, or even 5 years, they would have fucking revolted. 30 years is long enough to enter the workforce, and then retire, or die, or whatever. That's a long fucking time to build one building. Imagine that your parents started working on a pyramid the year you were born: by the time they were done, you'd already be experiencing an existential crisis from your dead-end job and worrying about your parents' mortality.