Imagine coming all the way to a planet light years away and making them awe inspiring monuments just for them to say 'yeah that's easy we could do that, in fact we did! We made this!'
Honestly though their fault for using their galaxy age tech to build something about as complex as your average bronze age civ...
[Jesus people, this is a joke as made obvious by the punchline about them building to a bronze age level - you guys really need to work on reading comprehension, it's such an important life skill]