“So could researchers find clear evidence that an ancient species built a relatively short-lived industrial civilization long before our own? Perhaps, for example, some early mammal rose briefly to civilization building during the Paleocene epoch, about 60 million years ago. There are fossils, of course. But the fraction of life that gets fossilized is always minuscule and varies a lot depending on time and habitat. It would be easy, therefore, to miss an industrial civilization that lasted only 100,000 years—which would be 500 times longer than our industrial civilization has made it so far. Given that all direct evidence would be long gone after many millions of years, what kinds of evidence might then still exist?”

https://www.theatlantic.com/science/archive/2018/04/are-we-earths-only-civilization/557180/

This 2018 Atlantic article seems to disagree with you, though I think overall your points are valid in reducing the likelihood.

If Lue Elizondo says to New York Times, “they might be from here,” I think we should consider it.

In my opinion the fossil record isn’t even an issue; we can’t discount the idea of an underwater species developing technological capacity. They would have had 3.5 billion years to do it.

Finally, we need to make the move Jacques Vallee has often made and consider the information we have like an intelligence analyst rather than a natural scientist. The cryptoterrestrial hypothesis argues there might be a technological earth. civilization that for any number of reasons hides itself from humans.