> In the end, there's a pretty good chance aliens visited us already.

And other theories suggest they interbred with us, and that we are hybrids.

Perhaps it is assumed most people won't think about these questions and just accept the FUD fear uncertainty and doubt? Often crashing around military sites would suggest to me a way to cover up failed prototype craft that are being demonstrated to potential buyers.

Also, can't they wear clothes ? Looks like the only aliens we have here on Earth are little greens or little grays, but one thing in common: always naked.

Psychological effect perhaps? Fear makes people talk about a thing. I don't know why this would be done given this would not be useful for getting space defense funding. We barely spend anything on watching for dangerous asteroids and that is not even a theoretical risk. Maybe it's as simple as distracting from current events? I would expect visitors to be in space suits that double as armor to protect from the risk of not being accepted and to allow for acclimation to or isolation from our atmosphere. The carvings all around the world on megaliths suggest that previous visitors wore space suits that had pseudo-wings and tanks but maybe they were just smoking some funny stuff or perhaps those were not aliens but just our own advanced civilization that mostly destroyed itself.

It's taken their entire life to get here expecting to find intelligent life and found us instead. It's suicide.

In God's geometry there is likely no way to say "faster than light" and we talk about it because we learned Newtonian physics before relativity.

Thus we (the life forms of this universe) are stuck with interstellar travel methods that require large amounts of time and energy. There has lately been the positive development that we think now we can stop at our destination with an artificial magnetosphere that creates drag with the interstellar medium, but it is hard. I'd imagine it takes 10,000 years to make it to a a nearby star and involves mastering deuterium-deuterium fusion. Instead of making the trip in one long shot, it would be possible to stop for fuel at comets, rouge planets, etc. along the way.

It seems to me that anyone who mastered that kind of technology might not care much about dry inner solar system planets when they could cut a planet like Pluto into pieces and construct a much larger habitat (room for trillions of people.) They very much may develop a comfortable lifestyle between the stars and in outer solar systems and just not care.

Imagine someone spent 10,000 years traveling between the stars and wanted to land on an Earth-like planet: they'd have the technology they needed for the journey, but they'd need some kind of "space shuttle" specialized for landing on an Earth-like planet. It doesn't make sense to carry one with them, if they are lucky they have plans to 3-d print one, but they possibly optimized their 3-d printers for making fusion system parts and other things they needed and maybe the old plans don't work. What's clear is that nobody has done such a thing for longer than humans have had civilization so the project of landing on Earth and returning to their "mothership" would be as formidable as us developing a space shuttle.

There are ideas like: "lets build self-replicating machines and fill up the galaxy with them" but that has to be tempered it being a high risk and zero reward project (e.g. by the time these start returning data maybe all your successors are dead or have changed so much you could care less what happens to them)

The easiest kind of meaningful interstellar communication might be a destructive attack with high-speed projectiles. Breakthrough Starshot was planning to launch a single microchip, but the energy content would be similar to a 1 megaton hydrogen bomb. If that hit a planet it would explode in the atmosphere and do little damage on the ground, but something scaled up could be quite dangerous. There's a case that we should make no effort to broadcast signals to other stars because it could well make us a target, the same could be true about other projects such as replicator probes. Playing it safe could be playing it quiet.