Okay, get ready to laugh. I believe it is some kind of shell game. We are forced to look at something - UFO's - in one area while somewhere else, the government is doing something else. What is that something else? I believe it is genetic engineering. Trying to create the perfect human, or trying to create things for one specific purpose. Drones and such. Trying to create the super-soldier. Maybe I've read too many comix. Anyway, while people are looking at Area 51 and thinking the government has aliens and such stashed away in there, I think they are working on something completely different in some other area.
I have no doubt that such things are part of the UFO phenomena.
It's full of complexity and nefarious goals and projects, imho.
That would require the "government" to be decades ahead of public science in the biomedical fields, which is impossible. The government spends billions to remain just a few years ahead in select fields like cryptography and satellite imaging, and we still know about those projects as many aspects must be carried out with private companies, and researchers that have security agreements and the like.
Biology is a much "messier" science than these others, and to jump as far ahead as you suggest would cost trillions, if it were possible anyway, which it probably isn't because, in contrast to something like cryptology, there's too much "interconnection" and mutual dependencies of the technologies and techniques that would be involved. It would involve MUCH larger projects than cryptology, satellite imaging, radars, and the like, and would be totally impossible to keep secret.