|>>|| No. 4832
I'll get the boring perspective out of the way: statistically speaking, other forms of life must exist, just in terms of raw numbers and the sheer scale of the universe. No, I don't believe we have been visited or contacted by these. "Ancient aliens" narratives remind me of theology, in the sense that we explain things with a powerful external force rather than make sense the complex reality.
I also disagree with your idea that beliefs about flying saucers or men in black were somehow better, or that older /boo/-type theories were generally more sensible in the past.
To take things meta-/boo/, I do genuinely think that a lot of what are called "conspiracy theories" are encouraged by military and security agencies to distract from issues which pose a genuine threat, or expose real agendas. I wish I could find it, but I'm sure I've read somewhere that the FBI encouraged rampant speculation about the JFK assassination and UFOs in the 1960s to draw attention away from Cointelpro -- a true conspiracy involving propaganda and outright murder of U.S. citizens.
It may be tempting to believe that there are grand and surprising truths being hidden somewhere, but the primary concern of "intelligence" agencies is the preservation of power. One way of doing that is to encourage outlandish and cultish behaviours -- even better if they're presented as forbidden knowledge only the privileged few or the super smart have access to. The U.S. has always had a deeply fearful and indoctrinated culture, going right back to the days of the Committee on Public Information and the Red Scare, and given that they largely dominate communication technologies (including the internet), we're exposed to those same traits. Real conspiracies do certainly exist, but they're so mundane that no one talks about them -- a high level meeting at BP or ExxonMobil is largely off-limits to the public and has world-changing implications, but we don't call that conspiracy.
Anyway, if you put aside all the /boo/ nonsense, there have been serious scientists debating the existence of aliens based on the evidence that we have. One of the most famous and informative debates was between Carl Sagan and Ernst Mayr. Sagan argued there must be intelligent aliens judging by the size of the universe, Mayr was a biologist who argued that we should look at the life we know -- and their tendency to die out before reaching the intelligence necessary to communicate across planets.