“I’m not of the view that ETs are thousands or millions of years in advance of us.”
given where we are on our understanding of the biomolecular mechanical foundations of Earth life, general knowledge, technology, AND the exponential trajectory of our accretion of same, ourselves and our terrasphere could have easily been made by a group only a few hundred years more advanced than us.
However, there’s the discrepant issue that the terraforming of Earth itself took hundreds of millions of our years (unless some kind of time warp was involved), which leads me to believe that the group could be quite old assuming it existed throughout the terraforming. I also strongly suspect that when the group started (assuming it was one group), it proceeded in an incremental fashion, advancing its knowledge and technology just like we do, and that they started with making viruses, then single cell animals, making ever more complex biomolecular creatures and systems, each step of the way based on the previous steps. That is, when they were making single cell animals, they had no idea how to make a homo sapiens, just as when we made the first transistor, we had no concept of the Internet, the integrated circuit, the CPU, the laptop, or Windows 7 Pro x64.
The wildest theory I have heard is that the grey ETs are demonically possessed but can be repelled by invoking the name and power of Jesus Christ. More measured if still cautionary views are offered by French scientist Jacques Vallée, who describes UFOs as "messengers of deception," and history professor David Jacobs, who sees UFOs as here for their own purposes, which, pursued without our consent, are almost certainly contrary to our interests. Others distinguish the so-called Nordic ETs are genuinely friendly toward humanity.
Some theorize that ETs are from a future version of humanity or a breakaway civilization that originated on Earth ages past. Then there is Jim Sparks, who claims to have begun as a resistant abductee to a cooperative one due to the ET message that we are killing the Earth because of our destructive practices toward the environment.
The UFO/ET subject is fascinating but offers little in the way of solid evidence. Mundane, day to day pursuits are in the end more compelling.
Some of them appear to be able to have grown us in fish farms. :^) (borrowed from the “Tripods” TV series).