I doubt there's anything we humans possess, that can't be had in great abundance, throughout the cosmos. A race so advanced that they'd harnessed the technology to shrink time and space wouldn't need to take anything from this third-rate mud ball of a planet.
I have a few theories on that, which dovetail into why the universe seems so quiet to research efforts such as SETI.
I think that SETI is monitoring the wrong sort of frequencies. I highly doubt that ET uses the radio band to communicate. I won't venture a guess as to what carrier wave they might be using, but if SETI were to stumble across it, I think they'd be overwhelmed with the volume of traffic "out there".
That may be, and I would hope that such would be the case. But beyond sheer material needs, I am of the opinion that if a lifeform reaches sufficient intelligence to where it can destroy itself as a species, it must also, as a race, master itself in terms of its animal origins. View it as a test of sorts, and most races fail, as humanity very well may, animal nature and its difficulties being what it is. That would make for a bit of quiet... although I would also agree with you that whatever methods of communication such races use, it is probably designed to be undetectable.
Those races that do manage to survive themselves would behave in a benign fashion, neither helping or hindering, allowing other species to follow their own course. I would like to think that creatures of a sufficiently advanced nature would not need for anything, nor be disposed to take what they need by force if that wasn't the case.
There's one more bit you mentioned about "cracking the physics puzzle" to allow interstellar transport. Something I note about all these various UFO sightings, which actually date back thousands of years, is that the basic geometry of these things hasn't changed in all that time. As you note, just look at how our own technologies have reshaped themselves over and over again within just the last 100 years. These things haven't change in over 2,000 years. Whatever they're using here, it appears to have hit the bottom of physics.