Where did the aliens come from that would have required faster than light travel and why don’t we have the technology (or at least the theory that demonstrably works) from it yet to do that ourselves?
Maybe we do...
Our plunge into the esoteric is only about 250 years in the making. Look how far we came in that time period. Assume "the others" didn't suffer a Dark Ages, and are 1400 years ahead of us. There is no reason to believe we know very much. Even Einstein said, "Knowledge is the measure of the radius of the sphere of ignorance".