Honestly, I have a rather particular approach to the UFO phenomenon. This Is my general vision:

Yes, UFOs exist.
Yes, some UFOs are extraterrestrial spacecrafts.
Yes, aliens visit Earth.
Yes, some UFOs crashed on Earth and have been recovered by Humans, specifically by the US Army and the Soviet/Russian Army.
Yes, the US and Russian armies tried to apply retro engineering to the crushed alien ships.
Yes, UFOs have been sighted even in ancient times.

However…

No, aliens have no hostile intentions.
No, Reptilians don’t exist. Stuff like that is just bulshit.
No, the aliens have never contacted anyone directly, either telepathically or face to face.
No, aliens have never abducted anyone.
No, aliens have never mutilated any cows.
No, crop circles are not aliens.
No, the reverse engineering on the crashed UFOs has never brought technological advances to the rest of the world, because they are still studying the crushed ships. They still don’t managed to successfully apply reverse engineering to any of the recovered crushed alien ships.
No, ancient astronauts don’t exist. The ancient civilizations developed by themselves, Zecharia Sitchin’s theories are bulshit and Eric Von Daniken is a liar. The fact that UFOs have been sighted even in ancient times doesn’t mean that the aliens contacted directly the ancient civilizations, nor that they built the Pyramids and bulshit like that.