But if we can't stop them then why haven't they attacked already? If aliens were here already, they had all this time to attack but didn't. I don't believe they are hostile.
They wouldn't travel all this way and wait for us to advance to then conquer us, it doesn't make sense. It's more likely they are advanced humans who work as one tribe, achieved the evolution of their people and society beyond ours.
It makes more sense that they are watching us waiting till we're ready for more advanced technology and open world views. Look how much the internet changed us yet some parts of our society is still barbaric, then imagine us with ufos. The world isn't unified, how would aliens fit into our daily lives. Would they solve war or world hunger or financial inequalities? Are they waiting for us to figure that out first?