I have a few fundamental premises that I apply to these questions regarding other intelligence and the prospects of us being visited in some way. Now, if you allow yourself to take this stuff too seriously, it starts to look a lot like religion, and I'm not a religious person. None of these thoughts are applied in any meaningful way to my everyday operation. I make no decisions based on the presumption that "they" are out there anywhere. But, I'm a sci-fi fan, I love technology, and I enjoy the mind-blowing aspect of cosmology so here's my thoughts...
I don't think we are anywhere close to a full understanding of the nature of the universe in a physics sense. In a cosmological time sense, we're infants. We have a lot to learn. Who knows what new understandings we'll have a thousand or ten-thousand or more years from now should we make it that far? So when it comes to things like FTL travel I don't assume that it's possible, but I don't assume that it's impossbile either. But, FTL travel isn't really even a necessity for any of this. I suspect that there isn't much need for biological specimens to buzz around the galaxy though. I figure that by the time we've (or any others have) figured out stuff like FTL travel, we'll also have figure out AI, and probably also "uploading" of consciousness. Our bodies will have been left behind and we'll exist in some other form. So the time necessary to get around becomes less of a problem in that situation.
I don't think we are alone in the galaxy. I think we are rare...but not alone.
[I often find myself out in nature just sort of taking in the ridiculous beauty of our world and I find it almost incomprehensibly unlikely that the "rules" exist in our universe for this planet to happen with its utter abundance of life literally EVERYWHERE and yet it only happens one single time in the entire cosmos. I just find that to be every bit as impossible as the idea that there is life everywhere in the cosmos. I basically believe in the mediocrity principle - our planet is likely neither the least-hospital nor the most-hospitable, and there's probably planets in this galaxy that are even more perfect for life than Earth.]
So, maybe there's currently a dozen or two dozen intelligent/technological species currently operating in our galaxy. Maybe there's 5. I imagine that over the past billion or more years, there's always some small number of intelligent/technological species operating in our galaxy...and in many other galaxies. Some of those don't get to our level of technology ever in their time. Some do. And maybe a few get beyond us - possibly even far beyond us. So, I suspect that there's probably a few intelligent species in our galaxy who've managed to reach a super-advanced tech level. They are very long-lived species...and they would be pretty damned "magical" from our perspective were we to somehow encounter them. Also, there has to be one advanced species that is more advanced than all the others. Somebody had to get there first. Maybe we're that species in our galaxy and perhaps that's our destiny- to become our galaxy's super-advanced beings...it's not impossible. But, if it's not us...it has to be somebody. There's a possibility that we are always under the scrutiny of a species that has attained a level of advancement such that they are actually monitoring the galaxy. It's something that would be of benefit to them (I mean if we could do that now would we not want to?)
I think maybe we have been visited in some sense. I don't have too much of a problem with the idea that some piece of alien tech could be active here. I don't even have much of a problem with the idea that it might have crashed here. I mean if we allow that there's other intelligent civs out there who have achieved the level of tech necessary to somehow get from star to star, then it's reasonable to assume that some of that tech would be "better-built" than other. Some of it would be the earliest steps in that endeavor and maybe it's less impervious to the rigors of getting around in space and more prone to glitches. Personally, I doubt the likelihood of little green men flittering around our planet. But, as I've said before - I don't have much of a problem with the possibility that AI-controlled probes could be doing so...and maybe a lot of them. They could be tiny. Hell, they could be smaller than a grain of sand. Who knows what might be possible on an atomic level.
Anyway, like I said...this is all just fun mind exercises for me. None of it impacts my life beyond that and I certainly don't walk around all day blathering on about aliens lol.