The ZOO hypothesis is uncannily attractive, because it a) sort-of humbles our egos and b) would actually be plausible even within humanity itself.

If we discovered another human civilization with a living and technological standard of Europe of 1022 AD, we would be able to keep an eye on them without revealing ourselves much. An occassional slip-up would be possible (a crashed drone), but most of the time, we would be able to let them live as they wish without interfering with them much. Probably to the point that the targeted civilization might consider any hypothesis of our surveillance a hoax or heresy.

And that is mere 1000 years of technological development on Earth. If the gap between us and hypothetical aliens is, say, 100 million years, I can't even begin to imagine the difference.

Something similar exists: https://en.wikipedia.org/wiki/North_Sentinel_Island

> 100 million years

That's a lot of evolution, considering mammals is barely that old.

not necessarily. UFOs might not hide intentionally; maybe they don't care but happen to rarely hang out in populated areas.

for instance, maybe they just care about the sea floor, and only surface to beam data back. or they're preferentially attracted to fast-moving objects like fighter jets, or sources of unusual EM signatures.

if UFOs are alien drones trying to hide, why do they suck at it?

Maybe they’re very good at it. We see them rarely and see them clearly or get good photos almost never but they’re actually all over the place. The ones we see are malfunctioning in some way or flukes caused by chance conditions of light, angle, etc.

Interesting points that I had completely overlooked!

By the way, without knowing how many there might be in total and how often they were seen/discovered, we can't really say if hiding from us is something they'd suck at :)