“would have had the technology and ability to dominate us decades ago.”
Why do you think they “have to” or “want to” dominate us?
Because this is how man thinks? “Got to win”? They are not men... Maybe they have no need or reason to “dominate us” and “win”. Win what?
These beings (if that is what they are) may see humans as nothing more than sensory mechanisms that can be occupied (or possessed) to enjoy the physical and emotional dimensions of this planet.
Why would any other civilization come here if it weren’t to befriend us or dominate. To travel that far without doing either seems pretty ridiculous, really.
What would they gain with secrecy?