Per UFO lore, the variety of craft, flight characteristics, inhabitants, etc. indicate a variety of species conducting 'scientific' studies, making Earth comparable to a sort of wildlife sanctuary. Quite the opposite of seeking to make contact, ET's are indifferent or reclusive, and contact is generally avoided except to take samples, to conduct tests, or to send a message.

The biggest surprise is that for all the physical evidence left behind, no extraterrestrial biological species have been noted or have become established. Given the history of how humans have unintentionally spread assorted pathogens or other species, it's hard to imagine the number and variety of extraterrestrials coming and going without accidentally contaminating the biosphere, now or in the past. Perhaps we are all made of exactly the same stuff, DNA, RNA, etc because it gets spread around? Or, the visitors have perfected the prevention of contamination?

It is hard to reconcile the uniform genetics of Earth life with the notion that multiple species are visiting.

On the other hand, UFO lore contains various mentions of those who encounter crashes or ET as perishing from illness shortly thereafter (Sverlovsk Midget, Coyame Mexico, and Varginha)

The US Navy and other services know these are not 'phenomena' but are structured machines. The pilots note that they exhibit performance characteristics that are significantly beyond the capabilities of known aircraft and contemporary nation-states.

Here's another video from Homeland Security which travels at a sustained velocity above 70 mph and is capable of underwater travel:

And one from the Chilean Navy:

While the Prime Directive is mostly in effect, the exceptions are notable: interference with ICBM electronics systems in the US and purportedly in Russia. Sustained surveillance of nuclear research and nuclear weapons storage sites is also notable.
A leaked letter from the estate of a Canadian envoy revealed that the US classified the subject higher than the hydrogen bomb.
Recently, emails recovered (from the estate of Neil Armstrong) validate the existence of ongoing deeply classified programs to study the issue.
However, neither we nor our elected officials are deemed to have a 'need to know' qualifying them for briefing.
It would be nice to get the other videos and reports generated by AATIP declassified, as the were the three videos released by DeLonge. Recovered materials held by Bigelow Aerospace are being studied and also indicate unknown technological fabrication techniques.

Debunkers wear their own foil hats with their mantra: Don't confuse me with facts, my mind is made up.