Mine is probably the most boring: There are many intelligent species in the universe. Faster-than-light travel, however, really is simply impossible, meaning that there cannot exist a truly interstellar civilization. So while some species have probably settled solar systems other than their own through generation ships, suspended animation, time dilation, or whatever, their range of expansion is limited. This means that encounters between species of different planets are rare. Humans will most likely never contact any intelligent alien species, at most one or two. We might, however, discover evidence of their existence through telescopes or something.
I reject it outright.
We've barely even begun to search, space is really big, and the technology we use for searching is still really not that very good. Looking at tiny sections of space with radio telescopes and shit and declaring that there's some big mystery about where all the aliens are is like dunking a shot glass into the ocean and wondering where all the fish are, the Fermi Paradox is nonsensical.
The question is not why we haven't found any alien life, it is why hasn't alien life found us? If they exist, then they are hiding themselves from us. Why? If they don't exist, why do we?
Well, the issue with the technology being used to search would apply to hypothetical eight billion year old aliens too, just in the opposite direction. All the signs we're giving off of being a technological intelligent species could simply be so obsolete they fly under the radar entirely, and while Earth would obviously be life-bearing we have no way of knowing if hypothetical aliens would care about that. Given that life might exist on Venus, I wouldn't be surprised if life is actually really common.
Also, I didn't mention this in my initial answer because I know what it does to my perceived credibility, but: UFOs are probably real. The US Navy has said as much, and more importantly a lot of people in the Scientific community are starting to care about the subject again, in recent years there have been more UFO-related scientific studies being set up than in the past few decades. The broad consensus among reputable people on the subject is that sufficient evidence exists to overturn the long-standing belief that UFOs aren't real, which was mostly created by the CIA-funded Condon Report which ignored it's own data and was made with the explicit purpose of 'disproving' UFOs, instead of being a genuine scientific study. Mainstream scientists are coming around to saying that it's a subject worthy of study, and while I don't know what UFOs are (and anyone who says they do is probably pulling some kind of grift) the ET hypothesis has remained popular for a number of good reasons. It's still unlikely, but the solution to the fermi paradox might be that they already have found us and we just took 80 years to figure that out.
I love that last sentence.
But, your solution to the Fermi Paradox is essentially that they aren't interested in us and we aren't smart enough to figure out where they are. Which, fair. But that is just a hypothesis that is untestable. There is no way for us to know if that is true, just like we can't prove if God exists. So, it's a neat idea, but kinda useless for solving the Fermi Paradox.
There's also the issue that life wouldn't have formed just 8 billion years ago. It would be evolving right now. On another planet, it would have evolved till human intelligence a million years before we did. On another, a billion years. Or really, any number between 0 to 8 billion years. Which means, just like life on Earth, life in the Milky Way would be in multiple stages.
Maybe the ones that are 8 billion years old have achieved nirvana and don't care about Earth, aren't curious about humanity, and don't want to harvest our Sun for energy. But can the same be said for species that are only a million years older than us?
Hell, Alpha Centauri is only 4 light years away from us, and there's a planet in the habitable zone there. So they would just need to travel a maximum of 4,000 years to reach us (if they can travel at the speed of our fastest probe). I mean, there are a bunch of other planets close enough to have life that has had enough time to reach us and that may be close to us in their evolutionary stage. That's the Fermi Paradox, if there is life anywhere else, why haven't we discovered it? Even if we're like bacteria to the Great Ones, there have to be other bacteria for whom we are food. **Where are they? **
ALSO, I wouldn't dismiss anyone for thinking UFOs are real. They might be. I hope they are.
After some thinking I don't really have an answer for the rest of your points on the Fermi Paradox, so fair enough.
Guess I'll just go all in on the UFOs then and point out the following: per this excellent paper (https://www.mdpi.com/1099-4300/21/10/939/htm) going over a number of quite credible UFO sightings that are - at minimum - radar-visual sightings, the objects in question displayed acceleration sufficient for interstellar travel by way of exploiting relativistic effects.
Even the slowest estimated acceleration among the objects would be able to (from their perspective) get from TRAPPIST-1 to here in only 58 days, and from Proxima Centuari to here in only 43. The highest acceleration observed, 5000 g, would mean that (from their perspective) it would take 1.4 days to get from Proxima Centauri to here, and 1.7 to get here from TRAPPIST-1.
If the sighted objects are aliens flying around, then if they didn't care about the timeskips (and there's many reasons they might not, maybe they don't age, maybe they're automated drones or robots, maybe they're nomadic, etc) that's a very workable speed for interstellar travel.
Ooh that paper looks exciting. Imma go give that a read. Thanks!
Part of the problem could be current technology. We blast radio waves into the ether, but those radio waves degrade over distance. Any radio we put out will be just background noise by the time it reaches an advanced alien civilization. It could be radio isn't even the dominant form of communication, so that's why we aren't receiving any kind of space chatter.
I wouldn't say that the Fermi Paradox is nonsensical. It's based on theories of habitable planets, age of the universe, and similar technological advancement in habitable planets. I agree there must be alien life out there, but it is strange to not see any clear signs yet. The galaxy is mapped, stars/planets move in an orderly fashion. Something very large moving in a way that doesn't make sense with it's gravitational orbit should be a clear sign of alien life. Hasn't happened.
Now why an alien species would make a dinner plate the size of a planet and attach thrusters to it is another question, but even so, you'd expect to see something.
Any K2 civilization would be observable from earth, provided they've been K2 long enough for the light to have reached us.
Right, exactly. To me, the fact that we haven't seen any evidence of megastructures suggests that there cannot exist such a thing as a K2 civilization, or anything particularly close. We can see millions/billions (not sure on the #, see below) of stars, but apparently not one sign of a megastructure. This is a much broader sample size than with conventional SETI listening for radio messages. I'm confident that if even one megastructure has ever been built in the history of the universe, there would be at least one that we could see.
Or at least that's what I was going to say, but apparently only 10,000 stars are visible to astronomers, which is a fairly small sample size. So who knows.Wait, what? With telescopes and shit there's no way we can only see that few.
Oh wait, I misread the search results. 10,000 is the total number that can seen from (all points combined on the) Earth by the naked eye. I can't find a number for, say, the Hubble, but it seems to be much higher.