"The masonry example was not a good one because it's too simple
. . .
I personally can't think of one that even comes close
. . .
why wouldn't they expect future humans to believe and learn more about them, and start to share the universe with them...?"
By masonry I thought you were referring to all masonry in general, the majority of which is much easier to understand how it was done than the other examples which so far we have no idea how they were done. I'm aware that there are those types scattered around the world, and the fact that it appears either the builders or people who made use of them made referrence to beings from other worlds on and/or near them seems very significant to me. The fact that there are a number of examples of constructions we can't explain today scattered out around the planet means people at some point either lost the ability to move huge rocks around somehow, and if so how and why? Or they all happened to unlearn somehow? They just all all of a sudden forgot? And then no one else was ever able to figure it out again exept one guy? If all of that was somehow the actual situation, wouldn't it be even weirder than for advanced beings to have visited this planet as well as all the other ones they've been to?
The ancient people told us that other beings came around and it appears that more advanced beings did help those ancient people, so I can't help but consider that the ancient people were not lying. Also, I still believe the ancient peope would expect future people (us) to know more about the advanced beings by this time, not less. So they would not be as? likely to lie on their monuments and sacred structures as they might be?? if they thought they would be able to fool people if they did...??? It just doesn't make sense that they would even try or that the thought would even enter their minds.