Technological assistance has been given, via humans, but the lines are drawn to where the influence, the result, would not remove humans from their essential task at hand which is to determine their spiritual orientation. In spiritual development, 3rd Density is the earliest, which you can equate to early grade school. Children are not allowed into the air traffic control tower nor the computer room, nor are they given guns - even when they understand how to work the equipment. Where you would not let a youngster into the air traffic control room, a young adult is allowed. The difference is that he has grown past the point where he thinks the world revolves around him, and is aware of how his actions affect others. You are not there yet, as an intelligent species.
Rumor has it that the secretive development of the Aurora and the recently emergent Stealth Bomber reflect a contribution of alien technology, and rumor is correct. This is not our technology, but was an early gift from ambassadors in the Service-to-Self who were busily bribing their way into the hearts of the military. Wildly enthusiastic and anticipating even greater coups, the military leadership at that time sold this program to whomever held the purse strings and set about becoming, so they presumed, the masters of the Earth.
The technology delivered, which had been demonstrated with alien space craft, did not work on human machines. Literally decades passed before the truth dawned on the deeply disappointed leadership - they had been deceived. The demonstration, which involved radar evasion, did not involve the shape or speed or surface material, as they had been told. The demonstration used density shifting, at speeds that the eye could not follow, so the disappearing ships, coming straight into the radar screens, seemed to have evaded radar. Right shape, right speed, and bingo, radar evasion. Needless to say, having touted the program, the sponsors were obliged to deliver something. All that money and time, searching after the right shape and speed, did result in a semblance of radar evasion. Why has the Aurora not been unveiled? Shame. It doesn't work as promoted, and as long as it is still under wraps the jury is still, theoretically, out.
Has really worthwhile technology been handed to the government? Absolutely not, as those in the Service-to-Self have no desire to see their recruits get out of hand, nor would they be allowed to interfere with the balance between humans here on Earth, by the Rule of Non-Interference, and those in the Service-to-Others would never encourage a war machine.