Just as in any other field of research or industry, there are those who are on the honest and true end of the spectrum and those who are on the other end, as well as all those who fall somewhere within the spectrum.
The spread of the spectrum within any given field of research or industry is often enough influenced by additional factors such as, public safety regulations, financing, law, etc..
Unfortunately, the field of research regarding the class containing alien knowledge and technology and application of, and within the public view, is biased away from the honest and true side of the spectrum. Not to say there is not honest and true research findings available to the public, but that in searching for it you will find more that doesn't fit that end of the spectrum but at best falls into the category of speculation and worse, total fabrication for personal agendas, disinformation and con for profit. And further but even more unfortunately, there are those who will feed off genuine research, distorting it as they see to fit their personal agendas. This does not help the public find clarity in drawing the line between the erroneous and honest information.
So what is one who has a genuine interest in understanding the honesty of the subject matter, to do?
Of course personal experience is where one may start, but even here it may be worth pursuing some sort of verification, if there is any question of whether a personal experience really happened of not.
Otherwise, and even in consideration of, a lack of undeniable evidence, the thing to do is to put effort into understanding the big question of why? Why are there claims of aliens encounters, abductions, knowledge, technology and even applications of, but such a great lack of proof relevant to the amount of claims?
Perhaps that is a question at the top of a pyramid, where the honest answer is far wider and deeper in scope than the question would seem to ask for.
Before going into available evidence let's touch on a few things, make a few assumptions but only to help draw a theory so to see if the evidence fits and to help us to know where to look to perhaps find such evidence.
For those who don't know or recall personally, knowledge of alien existence or related knowledge and/or technology:
1) Assume they do exist and that they have been here for quite some time.
2) Assume any conspiracy theories you may come across in the search and consideration of evidence, are of no primary value. We are not seeking to be distracted by conspiracy, but seeking evidence that helps us answer the big question of why, as indicated above.
3) Assume that any knowledge and/or technology that we don't already have due our own R&D will not be given to us by them (aliens). Assume the reason is simply because it its not in our scope of understanding and ability to make proper use of yet. We have to advance on our own.
4) Assume, regarding knowledge, that we can be inspired to put together what we have. What we already have within human knowledge can be brought to our individual attention. And any summed knowledge is within our ability to understand and properly make use of.
So where might we begin to look for evidence that leads to answering the question?
History, archeology, human evolution in social changes due population growth.
Technology, both biological and technological, and rate of advancement of these.
Cosmology, Astronomy on the large scale. Particle physics on the very small scale.
We have enough of our own information/knowledge to compile for an answer and not just a potentially valid answer but an obvious and certain answer with further expectations to extrapolate.