It is possible that some Orishas are physical extraterrestrials, where others are spirits or higher dimensional beings, and still others forces of nature to which we apply personalities so as to better understand them. We can speculate, but it is difficult for anyone to say who is who or what objectively. Each person who has experienced something can only speak from their own perspective.
One should approach this in terms of what works. The most well known Orishas have endured time, human forgetfulness and ungratefulness, cultural upheaval, political opposition, and competing belief systems. Those are invariably forces of nature who, though an alien could just as easily speak for them or be ridden by them as a human, are more than whatever physical body they may be using at the moment.
Another thing to consider is that if visiting beings could survive our atmosphere and live among us for any length of time, it’s likely that they’d be essentially human. Though they may have been from a different planet and have further advanced technology, they’d be people. It’s not too far fetched to think that without any regulations but their own sense of ethics, some may have come to our world for a visit or to stay. Genetically, they’d have evolved similarly though, so it takes nothing away from the Orishas if humans or any other kinds of beings visited us. They’re subject to the same laws of nature that we are, and when they die, the worms eat them the same as us.
The problem with alien intervention theory is that it could be demeaning to human genius and will. Scientists have found chimpanzees who make tools, and whales who cooperate. Is it really too much to think that a very intelligent human could have figured out that friction makes heat that can make fire?