We know very little of the limitations to demons and fallen angels to make much of their physical methodologies employed.
I also do agree, much of the population is heavily influenced by demonic activity and a smaller but growing portion are imo literally possessed now.
That is exactly why the demonic assessment of ETs seems unlikely to me. Considering the existence of ET entities IS NOT the source of evil on this planet. They might be quite the opposite, or they might just be wayfarers from a different corner of Creation.